<?php
/**
 * Adds a value to cache.
 *
 * If the specified key already exists, the value is not stored and the function
 * returns false.
 *
 * @link https://www.php.net/manual/en/memcached.add.php
 *
 * @param string $key        The key under which to store the value.
 * @param mixed  $value      The value to store.
 * @param string $group      The group value appended to the $key.
 * @param int    $expiration The expiration time, defaults to 0.
 * @return bool True on success, false on failure.
 */
function wp_cache_add( $key, $value, $group = '', $expiration = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->add( $key, $value, $group, $expiration );
}

/**
 * Adds a value to cache on a specific server.
 *
 * Using a server_key value, the object can be stored on a specified server as opposed
 * to a random server in the stack. Note that this method will add the key/value to the
 * _cache object as part of the runtime cache. It will add it to an array for the
 * specified server_key.
 *
 * @link https://www.php.net/manual/en/memcached.addbykey.php
 *
 * @param string $server_key The key identifying the server to store the value on.
 * @param string $key        The key under which to store the value.
 * @param mixed  $value      The value to store.
 * @param string $group      The group value appended to the $key.
 * @param int    $expiration The expiration time, defaults to 0.
 * @return bool True on success, false on failure.
 */
function wp_cache_add_by_key( $server_key, $key, $value, $group = '', $expiration = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->addByKey( $server_key, $key, $value, $group, $expiration );
}

/**
 * Adds a single server to the list of Memcached servers.
 *
 * @link https://www.php.net/manual/en/memcached.addserver.php
 *
 * @param string $host   The hostname of the memcache server.
 * @param int    $port   The port on which memcache is running.
 * @param int    $weight The weight of the server relative to the total weight
 *                       of all the servers in the pool.
 * @return bool True on success, false on failure.
 */
function wp_cache_add_server( $host, $port, $weight = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->addServer( $host, $port, $weight );
}

/**
 * Adds an array of servers to the pool.
 *
 * Each individual server in the array must include a domain and port, with an optional
 * weight value: $servers = array( array( '127.0.0.1', 11211, 0 ) );
 *
 * @link https://www.php.net/manual/en/memcached.addservers.php
 *
 * @param array $servers Array of server to register.
 * @return bool True on success, false on failure.
 */
function wp_cache_add_servers( $servers ) {
	global $wp_object_cache;
	return $wp_object_cache->addServers( $servers );
}

/**
 * Appends data to an existing item.
 *
 * This method should throw an error if it is used with compressed data.
 * This is an expected behavior. Memcached casts the value to be appended to the initial value
 * to the type of the initial value. Be careful as this leads to unexpected behavior at times.
 * Due to how memcached treats types, the behavior has been mimicked in the internal cache to produce
 * similar results and improve consistency. It is recommended that appends only occur with data of
 * the same type.
 *
 * @link https://www.php.net/manual/en/memcached.append.php
 *
 * @param string $key   The key under which to store the value.
 * @param mixed  $value Must be string as appending mixed values is not well-defined.
 * @param string $group The group value appended to the $key.
 * @return bool True on success, false on failure.
 */
function wp_cache_append( $key, $value, $group = '' ) {
	global $wp_object_cache;
	return $wp_object_cache->append( $key, $value, $group );
}

/**
 * Appends data to an existing item by server key.
 *
 * This method should throw an error if it is used with compressed data.
 * This is an expected behavior. Memcached casts the value to be appended to the initial value
 * to the type of the initial value. Be careful as this leads to unexpected behavior at times.
 * Due to how memcached treats types, the behavior has been mimicked in the internal cache to produce
 * similar results and improve consistency. It is recommended that appends only occur with data of
 * the same type.
 *
 * @link https://www.php.net/manual/en/memcached.appendbykey.php
 *
 * @param string $server_key The key identifying the server to store the value on.
 * @param string $key        The key under which to store the value.
 * @param mixed  $value      Must be string as appending mixed values is not well-defined.
 * @param string $group      The group value appended to the $key.
 * @return bool True on success, false on failure.
 */
function wp_cache_append_by_key( $server_key, $key, $value, $group = '' ) {
	global $wp_object_cache;
	return $wp_object_cache->appendByKey( $server_key, $key, $value, $group );
}

/**
 * Performs a "check and set" to store data.
 *
 * The set will be successful only if the no other request has updated the value
 * since it was fetched by this request.
 *
 * @link https://www.php.net/manual/en/memcached.cas.php
 *
 * @param float  $cas_token  Unique value associated with the existing item. Generated by memcached.
 * @param string $key        The key under which to store the value.
 * @param mixed  $value      The value to store.
 * @param string $group      The group value appended to the $key.
 * @param int    $expiration The expiration time, defaults to 0.
 * @return bool True on success, false on failure.
 */
function wp_cache_cas( $cas_token, $key, $value, $group = '', $expiration = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->cas( $cas_token, $key, $value, $group, $expiration );
}

/**
 * Performs a "check and set" to store data with a server key.
 *
 * The set will be successful only if the no other request has updated the value
 * since it was fetched by this request.
 *
 * @link https://www.php.net/manual/en/memcached.casbykey.php
 *
 * @param string $server_key The key identifying the server to store the value on.
 * @param float  $cas_token  Unique value associated with the existing item. Generated by memcached.
 * @param string $key        The key under which to store the value.
 * @param mixed  $value      The value to store.
 * @param string $group      The group value appended to the $key.
 * @param int    $expiration The expiration time, defaults to 0.
 * @return bool True on success, false on failure.
 */
function wp_cache_cas_by_key( $cas_token, $server_key, $key, $value, $group = '', $expiration = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->casByKey( $cas_token, $server_key, $key, $value, $group, $expiration );
}

/**
 * Closes the cache.
 *
 * This function has ceased to do anything since WordPress 2.5.
 * The functionality was removed along with the rest of the persistent cache.
 * This does not mean that plugins can't implement this function when they need
 * to make sure that the cache is cleaned up after WordPress no longer needs it.
 *
 * @since 2.0.0
 *
 * @return bool Always returns true.
 */
function wp_cache_close() {
	return true;
}

/**
 * Decrements a numeric item's value.
 *
 * @link https://www.php.net/manual/en/memcached.decrement.php
 *
 * @param string $key    The key under which to store the value.
 * @param int    $offset The amount by which to decrement the item's value.
 * @param string $group  The group value appended to the $key.
 * @return int|bool Item's new value on success, false on failure.
 */
function wp_cache_decrement( $key, $offset = 1, $group = '' ) {
	global $wp_object_cache;
	return $wp_object_cache->decrement( $key, $offset, $group );
}

/**
 * Decrements a numeric item's value.
 *
 * This is the same as wp_cache_decrement(), but kept for backward compatibility.
 * The original WordPress caching backends use wp_cache_decr().
 *
 * @link https://www.php.net/manual/en/memcached.decrement.php
 *
 * @param string $key    The key under which to store the value.
 * @param int    $offset The amount by which to decrement the item's value.
 * @param string $group  The group value appended to the $key.
 * @return int|bool Item's new value on success, false on failure.
 */
function wp_cache_decr( $key, $offset = 1, $group = '' ) {
	return wp_cache_decrement( $key, $offset, $group );
}

/**
 * Removes the item from the cache.
 *
 * Removes an item from memcached with identified by $key after $time seconds.
 * The $time parameter allows an object to be queued for deletion without
 * immediately deleting. Between the time that it is queued and the time it's deleted,
 * add, replace, and get will fail, but set will succeed.
 *
 * @link https://www.php.net/manual/en/memcached.delete.php
 *
 * @param string $key   The key under which to store the value.
 * @param string $group The group value appended to the $key.
 * @param int    $time  The amount of time the server will wait to delete the item in seconds.
 * @return bool True on success, false on failure.
 */
function wp_cache_delete( $key, $group = '', $time = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->delete( $key, $group, $time );
}

/**
 * Removes the item from the cache by server key.
 *
 * Removes an item from memcached with identified by $key after $time seconds.
 * The $time parameter allows an object to be queued for deletion without
 * immediately deleting. Between the time that it is queued and the time it's deleted,
 * add, replace, and get will fail, but set will succeed.
 *
 * @link https://www.php.net/manual/en/memcached.deletebykey.php
 *
 * @param string $server_key The key identifying the server to store the value on.
 * @param string $key        The key under which to store the value.
 * @param string $group      The group value appended to the $key.
 * @param int    $time       The amount of time the server will wait to delete the item in seconds.
 * @return bool True on success, false on failure.
 */
function wp_cache_delete_by_key( $server_key, $key, $group = '', $time = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->deleteByKey( $server_key, $key, $group, $time );
}

/**
 * Fetches the next result.
 *
 * @link https://www.php.net/manual/en/memcached.fetch.php
 *
 * @return array|false The next result on success, false on failure.
 */
function wp_cache_fetch() {
	global $wp_object_cache;
	return $wp_object_cache->fetch();
}

/**
 * Fetches all remaining results from the last request.
 *
 * @link https://www.php.net/manual/en/memcached.fetchall.php
 *
 * @return array|false The results on success, false on failure.
 */
function wp_cache_fetch_all() {
	global $wp_object_cache;
	return $wp_object_cache->fetchAll();
}

/**
 * Invalidates all items in the cache.
 *
 * @link https://www.php.net/manual/en/memcached.flush.php
 *
 * @param int $delay Number of seconds to wait before invalidating the items.
 * @return bool True on success, false on failure.
 */
function wp_cache_flush( $delay = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->flush( $delay );
}

/**
 * Retrieves object from cache.
 *
 * Gets an object from cache based on $key and $group. In order to fully support
 * the $cache_cb and $cas_token parameters, the runtime cache is ignored by this function
 * if either of those values are set. In that case, the request is made directly
 * to the memcached server for proper handling of the callback and/or token.
 *
 * Note that the $deprecated and $found args are only here for compatibility
 * with the native wp_cache_get() function.
 *
 * @link https://www.php.net/manual/en/memcached.get.php
 *
 * @param string      $key       The key under which to store the value.
 * @param string      $group     The group value appended to the $key.
 * @param bool        $force     Whether or not to force a cache invalidation.
 * @param null|bool   $found     Variable passed by reference to determine if the value was found or not.
 * @param null|string $cache_cb  Read-through caching callback.
 * @param null|float  $cas_token The variable to store the CAS token in.
 * @return bool|mixed Cached object value.
 */
function wp_cache_get( $key, $group = '', $force = false, &$found = null, $cache_cb = null, &$cas_token = null ) {
	global $wp_object_cache;

	if ( func_num_args() > 4 ) {
		return $wp_object_cache->get( $key, $group, $force, $found, '', false, $cache_cb, $cas_token );
	} else {
		return $wp_object_cache->get( $key, $group, $force, $found );
	}
}

/**
 * Retrieves object from cache from specified server.
 *
 * Gets an object from cache based on $key, $group, and $server_key. In order to fully support
 * the $cache_cb and $cas_token parameters, the runtime cache is ignored by this function
 * if either of those values are set. In that case, the request is made directly
 * to the memcached server for proper handling of the callback and/or token.
 *
 * @link https://www.php.net/manual/en/memcached.getbykey.php
 *
 * @param string      $server_key The key identifying the server to store the value on.
 * @param string      $key        The key under which to store the value.
 * @param string      $group      The group value appended to the $key.
 * @param bool        $force      Whether or not to force a cache invalidation.
 * @param null|bool   $found      Variable passed by reference to determine if the value was found or not.
 * @param null|string $cache_cb   Read-through caching callback.
 * @param null|float  $cas_token  The variable to store the CAS token in.
 * @return bool|mixed Cached object value.
 */
function wp_cache_get_by_key( $server_key, $key, $group = '', $force = false, &$found = null, $cache_cb = null, &$cas_token = null ) {
	global $wp_object_cache;

	if ( func_num_args() > 5 ) {
		return $wp_object_cache->getByKey( $server_key, $key, $group, $force, $found, $cache_cb, $cas_token );
	} else {
		return $wp_object_cache->getByKey( $server_key, $key, $group, $force, $found );
	}
}

/**
 * Requests multiple keys without blocking.
 *
 * @link https://www.php.net/manual/en/memcached.getdelayed.php
 *
 * @param string|array $keys     Array or string of key(s) to request.
 * @param string|array $groups   Array or string of group(s) for the key(s).
 *                               See buildKeys for more on how these are handled.
 * @param bool         $with_cas Whether to request CAS token values also.
 * @param null         $value_cb The result callback or null.
 * @return bool True on success, false on failure.
 */
function wp_cache_get_delayed( $keys, $groups = '', $with_cas = false, $value_cb = null ) {
	global $wp_object_cache;
	return $wp_object_cache->getDelayed( $keys, $groups, $with_cas, $value_cb );
}

/**
 * Requests multiple keys without blocking from a specified server.
 *
 * @link https://www.php.net/manual/en/memcached.getdelayed.php
 *
 * @param string       $server_key The key identifying the server to store the value on.
 * @param string|array $keys       Array or string of key(s) to request.
 * @param string|array $groups     Array or string of group(s) for the key(s).
 *                                 See buildKeys for more on how these are handled.
 * @param bool         $with_cas   Whether to request CAS token values also.
 * @param null         $value_cb   The result callback or null.
 * @return bool True on success, false on failure.
 */
function wp_cache_get_delayed_by_key( $server_key, $keys, $groups = '', $with_cas = false, $value_cb = null ) {
	global $wp_object_cache;
	return $wp_object_cache->getDelayedByKey( $server_key, $keys, $groups, $with_cas, $value_cb );
}

/**
 * Gets multiple values from memcached in one request.
 *
 * See the buildKeys method definition to understand the $keys/$groups parameters.
 *
 * @link https://www.php.net/manual/en/memcached.getmulti.php
 *
 * @param array        $keys       Array of keys to retrieve.
 * @param string|array $groups     If string, used for all keys.
 *                                 If arrays, corresponds with the $keys array.
 * @param null|array   $cas_tokens The variable to store the CAS tokens for the found items.
 * @param int          $flags      The flags for the get operation.
 * @return bool|array The array of found items on success, false on failure.
 */
function wp_cache_get_multi( $keys, $groups = '', &$cas_tokens = null, $flags = null ) {
	global $wp_object_cache;

	if ( func_num_args() > 2 ) {
		return $wp_object_cache->getMulti( $keys, $groups, '', $cas_tokens, $flags );
	} else {
		return $wp_object_cache->getMulti( $keys, $groups );
	}
}

/**
 * Gets multiple values from memcached in one request by specified server key.
 *
 * See the buildKeys method definition to understand the $keys/$groups parameters.
 *
 * @link https://www.php.net/manual/en/memcached.getmultibykey.php
 *
 * @param string       $server_key The key identifying the server to store the value on.
 * @param array        $keys       Array of keys to retrieve.
 * @param string|array $groups     If string, used for all keys.
 *                                 If arrays, corresponds with the $keys array.
 * @param null|array   $cas_tokens The variable to store the CAS tokens for the found items.
 * @param int          $flags      The flags for the get operation.
 * @return bool|array The array of found items on success, false on failure.
 */
function wp_cache_get_multi_by_key( $server_key, $keys, $groups = '', &$cas_tokens = null, $flags = null ) {
	global $wp_object_cache;

	if ( func_num_args() > 3 ) {
		return $wp_object_cache->getMultiByKey( $server_key, $keys, $groups, $cas_tokens, $flags );
	} else {
		return $wp_object_cache->getMultiByKey( $server_key, $keys, $groups );
	}
}

/**
 * Retrieves a Memcached option value.
 *
 * @link https://www.php.net/manual/en/memcached.getoption.php
 *
 * @param int $option One of the Memcached::OPT_* constants.
 * @return mixed The value of the requested option on success, false on failure.
 */
function wp_cache_get_option( $option ) {
	global $wp_object_cache;
	return $wp_object_cache->getOption( $option );
}

/**
 * Returns the result code of the last option.
 *
 * @link https://www.php.net/manual/en/memcached.getresultcode.php
 *
 * @return int Result code of the last Memcached operation.
 */
function wp_cache_get_result_code() {
	global $wp_object_cache;
	return $wp_object_cache->getResultCode();
}

/**
 * Return the message describing the result of the last operation.
 *
 * @link https://www.php.net/manual/en/memcached.getresultmessage.php
 *
 * @return string Message describing the result of the last Memcached operation.
 */
function wp_cache_get_result_message() {
	global $wp_object_cache;
	return $wp_object_cache->getResultMessage();
}

/**
 * Gets server information by key.
 *
 * @link https://www.php.net/manual/en/memcached.getserverbykey.php
 *
 * @param string $server_key The key identifying the server to store the value on.
 * @return array Array with host, post, and weight on success, fales on failure.
 */
function wp_cache_get_server_by_key( $server_key ) {
	global $wp_object_cache;
	return $wp_object_cache->getServerByKey( $server_key );
}

/**
 * Gets the list of servers in the pool.
 *
 * @link https://www.php.net/manual/en/memcached.getserverlist.php
 *
 * @return array The list of all servers in the server pool.
 */
function wp_cache_get_server_list() {
	global $wp_object_cache;
	return $wp_object_cache->getServerList();
}

/**
 * Gets server pool statistics.
 *
 * @link https://www.php.net/manual/en/memcached.getstats.php
 *
 * @return array Array of server statistics, one entry per server.
 */
function wp_cache_get_stats() {
	global $wp_object_cache;
	return $wp_object_cache->getStats();
}

/**
 * Gets server pool memcached version information.
 *
 * @link https://www.php.net/manual/en/memcached.getversion.php
 *
 * @return array Array of server versions, one entry per server.
 */
function wp_cache_get_version() {
	global $wp_object_cache;
	return $wp_object_cache->getVersion();
}

/**
 * Increments a numeric item's value.
 *
 * @link https://www.php.net/manual/en/memcached.increment.php
 *
 * @param string $key    The key under which to store the value.
 * @param int    $offset The amount by which to increment the item's value.
 * @param string $group  The group value appended to the $key.
 * @return int|bool Item's new value on success, false on failure.
 */
function wp_cache_increment( $key, $offset = 1, $group = '' ) {
	global $wp_object_cache;
	return $wp_object_cache->increment( $key, $offset, $group );
}

/**
 * Increments a numeric item's value.
 *
 * This is the same as wp_cache_increment(), but kept for backward compatibility.
 * The original WordPress caching backends use wp_cache_incr().
 *
 * @link https://www.php.net/manual/en/memcached.increment.php
 *
 * @param string $key    The key under which to store the value.
 * @param int    $offset The amount by which to increment the item's value.
 * @param string $group  The group value appended to the $key.
 * @return int|bool Item's new value on success, false on failure.
 */
function wp_cache_incr( $key, $offset = 1, $group = '' ) {
	return wp_cache_increment( $key, $offset, $group );
}

/**
 * Prepends data to an existing item.
 *
 * This method should throw an error if it is used with compressed data. This is an expected behavior.
 * Memcached casts the value to be prepended to the initial value to the type of the initial value.
 * Be careful as this leads to unexpected behavior at times. For instance, prepending (float) 45.23
 * to (int) 23 will result in 45, because the value is first combined (45.2323) then cast to "integer"
 * (the original value), which will be (int) 45. Due to how memcached treats types, the behavior has been
 * mimicked in the internal cache to produce similar results and improve consistency. It is recommended
 * that prepends only occur with data of the same type.
 *
 * @link https://www.php.net/manual/en/memcached.prepend.php
 *
 * @param string $key   The key under which to store the value.
 * @param string $value Must be string as prepending mixed values is not well-defined.
 * @param string $group The group value prepended to the $key.
 * @return bool True on success, false on failure.
 */
function wp_cache_prepend( $key, $value, $group = '' ) {
	global $wp_object_cache;
	return $wp_object_cache->prepend( $key, $value, $group );
}

/**
 * Appends data to an existing item by server key.
 *
 * This method should throw an error if it is used with compressed data. This is an expected behavior.
 * Memcached casts the value to be prepended to the initial value to the type of the initial value.
 * Be careful as this leads to unexpected behavior at times. For instance, prepending (float) 45.23
 * to (int) 23 will result in 45, because the value is first combined (45.2323) then cast to "integer"
 * (the original value), which will be (int) 45. Due to how memcached treats types, the behavior has been
 * mimicked in the internal cache to produce similar results and improve consistency. It is recommended
 * that prepends only occur with data of the same type.
 *
 * @link https://www.php.net/manual/en/memcached.prependbykey.php
 *
 * @param string $server_key The key identifying the server to store the value on.
 * @param string $key        The key under which to store the value.
 * @param string $value      Must be string as prepending mixed values is not well-defined.
 * @param string $group      The group value prepended to the $key.
 * @return bool True on success, false on failure.
 */
function wp_cache_prepend_by_key( $server_key, $key, $value, $group = '' ) {
	global $wp_object_cache;
	return $wp_object_cache->prependByKey( $server_key, $key, $value, $group );
}

/**
 * Replaces a value in cache.
 *
 * This method is similar to "add"; however, is does not successfully set a value
 * if the object's key is not already set in cache.
 *
 * @link https://www.php.net/manual/en/memcached.replace.php
 *
 * @param string $key        The key under which to store the value.
 * @param mixed  $value      The value to store.
 * @param string $group      The group value appended to the $key.
 * @param int    $expiration The expiration time, defaults to 0.
 * @return bool True on success, false on failure.
 */
function wp_cache_replace( $key, $value, $group = '', $expiration = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->replace( $key, $value, $group, $expiration );
}

/**
 * Replaces a value in cache on a specific server.
 *
 * This method is similar to "addByKey"; however, is does not successfully set a value
 * if the object's key is not already set in cache.
 *
 * @link https://www.php.net/manual/en/memcached.addbykey.php
 *
 * @param string $server_key The key identifying the server to store the value on.
 * @param string $key        The key under which to store the value.
 * @param mixed  $value      The value to store.
 * @param string $group      The group value appended to the $key.
 * @param int    $expiration The expiration time, defaults to 0.
 * @return bool True on success, false on failure.
 */
function wp_cache_replace_by_key( $server_key, $key, $value, $group = '', $expiration = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->replaceByKey( $server_key, $key, $value, $group, $expiration );
}

/**
 * Sets a value in cache.
 *
 * The value is set whether or not this key already exists in memcached.
 *
 * @link https://www.php.net/manual/en/memcached.set.php
 *
 * @param string $key        The key under which to store the value.
 * @param mixed  $value      The value to store.
 * @param string $group      The group value appended to the $key.
 * @param int    $expiration The expiration time, defaults to 0.
 * @return bool True on success, false on failure.
 */
function wp_cache_set( $key, $value, $group = '', $expiration = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->set( $key, $value, $group, $expiration );
}

/**
 * Sets a value in cache.
 *
 * The value is set whether or not this key already exists in memcached.
 *
 * @link https://www.php.net/manual/en/memcached.set.php
 *
 * @param string $server_key The key identifying the server to store the value on.
 * @param string $key        The key under which to store the value.
 * @param mixed  $value      The value to store.
 * @param string $group      The group value appended to the $key.
 * @param int    $expiration The expiration time, defaults to 0.
 * @return bool True on success, false on failure.
 */
function wp_cache_set_by_key( $server_key, $key, $value, $group = '', $expiration = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->setByKey( $server_key, $key, $value, $group, $expiration );
}

/**
 * Sets multiple values to cache at once.
 *
 * By sending an array of $items to this function, all values are saved at once to
 * memcached, reducing the need for multiple requests to memcached. The $items array
 * keys and values are what are stored to memcached. The keys in the $items array
 * are merged with the $groups array/string value via buildKeys to determine the
 * final key for the object.
 *
 * @param array        $items      An array of key/value pairs to store on the server.
 * @param string|array $groups     Group(s) to merge with key(s) in $items.
 * @param int          $expiration The expiration time, defaults to 0.
 * @return bool True on success, false on failure.
 */
function wp_cache_set_multi( $items, $groups = '', $expiration = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->setMulti( $items, $groups, $expiration );
}

/**
 * Sets multiple values to cache at once on specified server.
 *
 * By sending an array of $items to this function, all values are saved at once to
 * memcached, reducing the need for multiple requests to memcached. The $items array
 * keys and values are what are stored to memcached. The keys in the $items array
 * are merged with the $groups array/string value via buildKeys to determine the
 * final key for the object.
 *
 * @param string       $server_key The key identifying the server to store the value on.
 * @param array        $items      An array of key/value pairs to store on the server.
 * @param string|array $groups     Group(s) to merge with key(s) in $items.
 * @param int          $expiration The expiration time, defaults to 0.
 * @return bool True on success, false on failure.
 */
function wp_cache_set_multi_by_key( $server_key, $items, $groups = 'default', $expiration = 0 ) {
	global $wp_object_cache;
	return $wp_object_cache->setMultiByKey( $server_key, $items, $groups, $expiration );
}

/**
 * Sets a Memcached option.
 *
 * @link https://www.php.net/manual/en/memcached.setoption.php
 *
 * @param int   $option Option name.
 * @param mixed $value  Option value.
 * @return bool True on success, false on failure.
 */
function wp_cache_set_option( $option, $value ) {
	global $wp_object_cache;
	return $wp_object_cache->setOption( $option, $value );
}

/**
 * Switches blog prefix, which changes the cache that is accessed.
 *
 * @param int $blog_id Blog to switch to.
 * @return void
 */
function wp_cache_switch_to_blog( $blog_id ) {
	global $wp_object_cache;
	return $wp_object_cache->switch_to_blog( $blog_id );
}


/**
 * Sets up Object Cache Global and assigns it.
 *
 * @global WP_Object_Cache $wp_object_cache WordPress Object Cache
 * @return void
 */
function wp_cache_init() {
	global $wp_object_cache;
	$wp_object_cache = new WP_Object_Cache();
}

/**
 * Adds a group or set of groups to the list of non-persistent groups.
 *
 * @param string|array $groups A group or an array of groups to add.
 * @return void
 */
function wp_cache_add_global_groups( $groups ) {
	global $wp_object_cache;
	$wp_object_cache->add_global_groups( $groups );
}

/**
 * Adds a group or set of groups to the list of non-Memcached groups.
 *
 * @param string|array $groups A group or an array of groups to add.
 * @return void
 */
function wp_cache_add_non_persistent_groups( $groups ) {
	global $wp_object_cache;
	$wp_object_cache->add_non_persistent_groups( $groups );
}

// phpcs:disable WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid
class WP_Object_Cache {

	/**
	 * Holds the Memcached object.
	 *
	 * @var Memcached
	 */
	public $m;

	/**
	 * Hold the Memcached server details.
	 *
	 * @var array
	 */
	public $servers;

	/**
	 * Holds the non-Memcached objects.
	 *
	 * @var array
	 */
	public $cache = array();

	/**
	 * List of global groups.
	 *
	 * @var array
	 */
	public $global_groups = array( 'users', 'userlogins', 'usermeta', 'site-options', 'site-lookup', 'blog-lookup', 'blog-details', 'rss' );

	/**
	 * List of groups not saved to Memcached.
	 *
	 * @var array
	 */
	public $no_mc_groups = array( 'comment', 'counts' );

	/**
	 * Prefix used for global groups.
	 *
	 * @var string
	 */
	public $global_prefix = '';

	/**
	 * Prefix used for non-global groups.
	 *
	 * @var string
	 */
	public $blog_prefix = '';

	/**
	 * Instantiates the Memcached class.
	 *
	 * Instantiates the Memcached class and returns adds the servers specified
	 * in the $memcached_servers global array.
	 *
	 * @link https://www.php.net/manual/en/memcached.construct.php
	 *
	 * @param null $persistent_id To create an instance that persists between requests,
	 *                            use persistent_id to specify a unique ID for the instance.
	 */
	public function __construct( $persistent_id = null ) {
		global $memcached_servers, $blog_id, $table_prefix;

		if ( is_null( $persistent_id ) || ! is_string( $persistent_id ) ) {
			$this->m = new Memcached();
		} else {
			$this->m = new Memcached( $persistent_id );
		}

		if ( isset( $memcached_servers ) ) {
			$this->servers = $memcached_servers;
		} else {
			$this->servers = array( array( 'memcached', 11211 ) );
		}

		$this->addServers( $this->servers );

		/**
		 * This approach is borrowed from Sivel and Boren. Use the salt for easy cache invalidation
		 * and for multi single WP installations on the same server.
		 */
		if ( ! defined( 'WP_CACHE_KEY_SALT' ) ) {
			define( 'WP_CACHE_KEY_SALT', '' );
		}

		// Assign global and blog prefixes for use with keys.
		if ( function_exists( 'is_multisite' ) ) {
			$this->global_prefix = ( is_multisite() || defined( 'CUSTOM_USER_TABLE' ) && defined( 'CUSTOM_USER_META_TABLE' ) ) ? '' : $table_prefix;
			$this->blog_prefix   = ( is_multisite() ? $blog_id : $table_prefix ) . ':';
		}

		// Setup cacheable values for handling expiration times.
		$this->thirty_days = 60 * 60 * 24 * 30;
		$this->now         = time();
	}

	/**
	 * Adds a value to cache.
	 *
	 * If the specified key already exists, the value is not stored and the function
	 * returns false.
	 *
	 * @link https://www.php.net/manual/en/memcached.add.php
	 *
	 * @param string $key        The key under which to store the value.
	 * @param mixed  $value      The value to store.
	 * @param string $group      The group value appended to the $key.
	 * @param int    $expiration The expiration time, defaults to 0.
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param bool   $by_key     True to store in internal cache by key; false to not store by key.
	 * @return bool True on success, false on failure.
	 */
	public function add( $key, $value, $group = 'default', $expiration = 0, $server_key = '', $by_key = false ) {
		/*
		 * Ensuring that wp_suspend_cache_addition is defined before calling, because sometimes an advanced-cache.php
		 * file will load object-cache.php before wp-includes/functions.php is loaded. In those cases, if wp_cache_add
		 * is called in advanced-cache.php before any more of WordPress is loaded, we get a fatal error because
		 * wp_suspend_cache_addition will not be defined until wp-includes/functions.php is loaded.
		 */
		if ( function_exists( 'wp_suspend_cache_addition' ) && wp_suspend_cache_addition() ) {
			return false;
		}

		$derived_key = $this->buildKey( $key, $group );
		$expiration  = $this->sanitize_expiration( $expiration );

		// If group is a non-Memcached group, save to runtime cache, not Memcached.
		if ( in_array( $group, $this->no_mc_groups, true ) ) {

			// Add does not set the value if the key exists; mimic that here.
			if ( isset( $this->cache[ $derived_key ] ) ) {
				return false;
			}

			$this->add_to_internal_cache( $derived_key, $value );

			return true;
		}

		// Save to Memcached.
		if ( $by_key ) {
			$result = $this->m->addByKey( $server_key, $derived_key, $value, $expiration );
		} else {
			$result = $this->m->add( $derived_key, $value, $expiration );
		}

		// Store in runtime cache if add was successful.
		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$this->add_to_internal_cache( $derived_key, $value );
		}

		return $result;
	}

	/**
	 * Adds a value to cache on a specific server.
	 *
	 * Using a server_key value, the object can be stored on a specified server as opposed
	 * to a random server in the stack. Note that this method will add the key/value to the
	 * _cache object as part of the runtime cache. It will add it to an array for the
	 * specified server_key.
	 *
	 * @link https://www.php.net/manual/en/memcached.addbykey.php
	 *
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param string $key        The key under which to store the value.
	 * @param mixed  $value      The value to store.
	 * @param string $group      The group value appended to the $key.
	 * @param int    $expiration The expiration time, defaults to 0.
	 * @return bool True on success, false on failure.
	 */
	public function addByKey( $server_key, $key, $value, $group = 'default', $expiration = 0 ) {
		return $this->add( $key, $value, $group, $expiration, $server_key, true );
	}

	/**
	 * Adds a single server to the list of Memcached servers.
	 *
	 * @link https://www.php.net/manual/en/memcached.addserver.php
	 *
	 * @param string $host   The hostname of the memcache server.
	 * @param int    $port   The port on which memcache is running.
	 * @param int    $weight The weight of the server relative to the total weight
	 *                       of all the servers in the pool.
	 * @return bool True on success, false on failure.
	 */
	public function addServer( $host, $port, $weight = 0 ) {
		$host   = is_string( $host ) ? $host : '127.0.0.1';
		$port   = is_numeric( $port ) && $port > 0 ? $port : 11211;
		$weight = is_numeric( $weight ) && $weight > 0 ? $weight : 1;

		return $this->m->addServer( $host, $port, $weight );
	}

	/**
	 * Adds an array of servers to the pool.
	 *
	 * Each individual server in the array must include a domain and port, with an optional
	 * weight value: $servers = array( array( '127.0.0.1', 11211, 0 ) );
	 *
	 * @link https://www.php.net/manual/en/memcached.addservers.php
	 *
	 * @param array $servers Array of server to register.
	 * @return bool True on success, false on failure.
	 */
	public function addServers( $servers ) {
		if ( ! is_object( $this->m ) ) {
			return false;
		}

		return $this->m->addServers( $servers );
	}

	/**
	 * Appends data to an existing item.
	 *
	 * This method should throw an error if it is used with compressed data.
	 * This is an expected behavior. Memcached casts the value to be appended to the initial value
	 * to the type of the initial value. Be careful as this leads to unexpected behavior at times.
	 * Due to how memcached treats types, the behavior has been mimicked in the internal cache to produce
	 * similar results and improve consistency. It is recommended that appends only occur with data of
	 * the same type.
	 *
	 * @link https://www.php.net/manual/en/memcached.append.php
	 *
	 * @param string $key        The key under which to store the value.
	 * @param mixed  $value      Must be string as appending mixed values is not well-defined.
	 * @param string $group      The group value appended to the $key.
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param bool   $by_key     True to store in internal cache by key; false to not store by key.
	 * @return bool True on success, false on failure.
	 */
	public function append( $key, $value, $group = 'default', $server_key = '', $by_key = false ) {
		if ( ! is_string( $value ) && ! is_int( $value ) && ! is_float( $value ) ) {
			return false;
		}

		$derived_key = $this->buildKey( $key, $group );

		// If group is a non-Memcached group, append to runtime cache value, not Memcached.
		if ( in_array( $group, $this->no_mc_groups, true ) ) {
			if ( ! isset( $this->cache[ $derived_key ] ) ) {
				return false;
			}

			$combined = $this->combine_values( $this->cache[ $derived_key ], $value, 'app' );
			$this->add_to_internal_cache( $derived_key, $combined );
			return true;
		}

		// Append to Memcached value.
		if ( $by_key ) {
			$result = $this->m->appendByKey( $server_key, $derived_key, $value );
		} else {
			$result = $this->m->append( $derived_key, $value );
		}

		// Store in runtime cache if add was successful.
		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$combined = $this->combine_values( $this->cache[ $derived_key ], $value, 'app' );
			$this->add_to_internal_cache( $derived_key, $combined );
		}

		return $result;
	}

	/**
	 * Appends data to an existing item by server key.
	 *
	 * This method should throw an error if it is used with compressed data.
	 * This is an expected behavior. Memcached casts the value to be appended to the initial value
	 * to the type of the initial value. Be careful as this leads to unexpected behavior at times.
	 * Due to how memcached treats types, the behavior has been mimicked in the internal cache to produce
	 * similar results and improve consistency. It is recommended that appends only occur with data of
	 * the same type.
	 *
	 * @link https://www.php.net/manual/en/memcached.appendbykey.php
	 *
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param string $key        The key under which to store the value.
	 * @param mixed  $value      Must be string as appending mixed values is not well-defined.
	 * @param string $group      The group value appended to the $key.
	 * @return bool True on success, false on failure.
	 */
	public function appendByKey( $server_key, $key, $value, $group = 'default' ) {
		return $this->append( $key, $value, $group, $server_key, true );
	}

	/**
	 * Performs a "check and set" to store data.
	 *
	 * The set will be successful only if the no other request has updated the value
	 * since it was fetched by this request.
	 *
	 * @link https://www.php.net/manual/en/memcached.cas.php
	 *
	 * @param float  $cas_token  Unique value associated with the existing item. Generated by memcached.
	 * @param string $key        The key under which to store the value.
	 * @param mixed  $value      The value to store.
	 * @param string $group      The group value appended to the $key.
	 * @param int    $expiration The expiration time, defaults to 0.
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param bool   $by_key     True to store in internal cache by key; false to not store by key.
	 * @return bool True on success, false on failure.
	 */
	public function cas( $cas_token, $key, $value, $group = 'default', $expiration = 0, $server_key = '', $by_key = false ) {
		$derived_key = $this->buildKey( $key, $group );
		$expiration  = $this->sanitize_expiration( $expiration );

		/**
		 * If group is a non-Memcached group, save to runtime cache, not Memcached. Note
		 * that since check and set cannot be emulated in the run time cache, this value
		 * operation is treated as a normal "add" for no_mc_groups.
		 */
		if ( in_array( $group, $this->no_mc_groups, true ) ) {
			$this->add_to_internal_cache( $derived_key, $value );
			return true;
		}

		// Save to Memcached.
		if ( $by_key ) {
			$result = $this->m->casByKey( $cas_token, $server_key, $derived_key, $value, $expiration );
		} else {
			$result = $this->m->cas( $cas_token, $derived_key, $value, $expiration );
		}

		// Store in runtime cache if cas was successful.
		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$this->add_to_internal_cache( $derived_key, $value );
		}

		return $result;
	}

	/**
	 * Performs a "check and set" to store data with a server key.
	 *
	 * The set will be successful only if the no other request has updated the value
	 * since it was fetched by this request.
	 *
	 * @link https://www.php.net/manual/en/memcached.casbykey.php
	 *
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param float  $cas_token  Unique value associated with the existing item. Generated by memcached.
	 * @param string $key        The key under which to store the value.
	 * @param mixed  $value      The value to store.
	 * @param string $group      The group value appended to the $key.
	 * @param int    $expiration The expiration time, defaults to 0.
	 * @return bool True on success, false on failure.
	 */
	public function casByKey( $cas_token, $server_key, $key, $value, $group = 'default', $expiration = 0 ) {
		return $this->cas( $cas_token, $key, $value, $group, $expiration, $server_key, true );
	}

	/**
	 * Decrements a numeric item's value.
	 *
	 * @link https://www.php.net/manual/en/memcached.decrement.php
	 *
	 * @param string $key    The key under which to store the value.
	 * @param int    $offset The amount by which to decrement the item's value.
	 * @param string $group  The group value appended to the $key.
	 * @return int|bool Item's new value on success, false on failure.
	 */
	public function decrement( $key, $offset = 1, $group = 'default' ) {
		$derived_key = $this->buildKey( $key, $group );

		// Decrement values in no_mc_groups.
		if ( in_array( $group, $this->no_mc_groups, true ) ) {

			// Only decrement if the key already exists and value is 0 or greater (mimics memcached behavior).
			if ( isset( $this->cache[ $derived_key ] ) && $this->cache[ $derived_key ] >= 0 ) {

				// If numeric, subtract; otherwise, consider it 0 and do nothing.
				if ( is_numeric( $this->cache[ $derived_key ] ) ) {
					$this->cache[ $derived_key ] -= (int) $offset;
				} else {
					$this->cache[ $derived_key ] = 0;
				}

				// Returned value cannot be less than 0.
				if ( $this->cache[ $derived_key ] < 0 ) {
					$this->cache[ $derived_key ] = 0;
				}

				return $this->cache[ $derived_key ];
			} else {
				return false;
			}
		}

		$result = $this->m->decrement( $derived_key, $offset );

		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$this->add_to_internal_cache( $derived_key, $result );
		}

		return $result;
	}

	/**
	 * Decrements a numeric item's value.
	 *
	 * Alias for $this->decrement(). Other caching backends use this abbreviated form
	 * of the function. It *may* cause breakage somewhere, so it is nice to have.
	 * This function will also allow the core unit tests to pass.
	 *
	 * @param string $key    The key under which to store the value.
	 * @param int    $offset The amount by which to decrement the item's value.
	 * @param string $group  The group value appended to the $key.
	 * @return int|bool Item's new value on success, false on failure.
	 */
	public function decr( $key, $offset = 1, $group = 'default' ) {
		return $this->decrement( $key, $offset, $group );
	}

	/**
	 * Removes the item from the cache.
	 *
	 * Removes an item from memcached with identified by $key after $time seconds.
	 * The $time parameter allows an object to be queued for deletion without
	 * immediately deleting. Between the time that it is queued and the time it's deleted,
	 * add, replace, and get will fail, but set will succeed.
	 *
	 * @link https://www.php.net/manual/en/memcached.delete.php
	 *
	 * @param string $key        The key under which to store the value.
	 * @param string $group      The group value appended to the $key.
	 * @param int    $time       The amount of time the server will wait to delete the item in seconds.
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param bool   $by_key     True to store in internal cache by key; false to not store by key.
	 * @return bool True on success, false on failure.
	 */
	public function delete( $key, $group = 'default', $time = 0, $server_key = '', $by_key = false ) {
		$derived_key = $this->buildKey( $key, $group );

		// Remove from no_mc_groups array.
		if ( in_array( $group, $this->no_mc_groups, true ) ) {
			if ( isset( $this->cache[ $derived_key ] ) ) {
				unset( $this->cache[ $derived_key ] );
			}

			return true;
		}

		if ( $by_key ) {
			$result = $this->m->deleteByKey( $server_key, $derived_key, $time );
		} else {
			$result = $this->m->delete( $derived_key, $time );
		}

		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			unset( $this->cache[ $derived_key ] );
		}

		return $result;
	}

	/**
	 * Removes the item from the cache by server key.
	 *
	 * Removes an item from memcached with identified by $key after $time seconds.
	 * The $time parameter allows an object to be queued for deletion without
	 * immediately deleting. Between the time that it is queued and the time it's deleted,
	 * add, replace, and get will fail, but set will succeed.
	 *
	 * @link https://www.php.net/manual/en/memcached.deletebykey.php
	 *
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param string $key        The key under which to store the value.
	 * @param string $group      The group value appended to the $key.
	 * @param int    $time       The amount of time the server will wait to delete the item in seconds.
	 * @return bool True on success, false on failure.
	 */
	public function deleteByKey( $server_key, $key, $group = 'default', $time = 0 ) {
		return $this->delete( $key, $group, $time, $server_key, true );
	}

	/**
	 * Fetches the next result.
	 *
	 * @link https://www.php.net/manual/en/memcached.fetch.php
	 *
	 * @return array|false The next result on success, false on failure.
	 */
	public function fetch() {
		return $this->m->fetch();
	}

	/**
	 * Fetches all remaining results from the last request.
	 *
	 * @link https://www.php.net/manual/en/memcached.fetchall.php
	 *
	 * @return array|false The results on success, false on failure.
	 */
	public function fetchAll() {
		return $this->m->fetchAll();
	}

	/**
	 * Invalidates all items in the cache.
	 *
	 * @link https://www.php.net/manual/en/memcached.flush.php
	 *
	 * @param int $delay Number of seconds to wait before invalidating the items.
	 * @return bool True on success, false on failure.
	 */
	public function flush( $delay = 0 ) {
		$result = $this->m->flush( $delay );

		// Only reset the runtime cache if memcached was properly flushed.
		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$this->cache = array();
		}

		return $result;
	}

	/**
	 * Retrieves object from cache.
	 *
	 * Gets an object from cache based on $key and $group. In order to fully support
	 * the $cache_cb and $cas_token parameters, the runtime cache is ignored by this function
	 * if either of those values are set. In that case, the request is made directly
	 * to the memcached server for proper handling of the callback and/or token.
	 * Note that the $cas_token variable cannot be directly passed to the function.
	 * The variable needs to be first defined with a non-null value.
	 *
	 * If using the $cache_cb argument, the new value will always have an expiration
	 * of time of 0 (forever). This is a limitation of the Memcached PECL extension.
	 *
	 * @link https://www.php.net/manual/en/memcached.get.php
	 *
	 * @param string        $key        The key under which to store the value.
	 * @param string        $group      The group value appended to the $key.
	 * @param bool          $force      Whether or not to force a cache invalidation.
	 * @param null|bool     $found      Variable passed by reference to determine if the value was found or not.
	 * @param string        $server_key The key identifying the server to store the value on.
	 * @param bool          $by_key     True to store in internal cache by key; false to not store by key.
	 * @param null|callable $cache_cb   Read-through caching callback.
	 * @param null|float    $cas_token  The variable to store the CAS token in.
	 * @return bool|mixed Cached object value.
	 */
	public function get( $key, $group = 'default', $force = false, &$found = null, $server_key = '', $by_key = false, $cache_cb = null, &$cas_token = null ) {
		$derived_key = $this->buildKey( $key, $group );

		// Assume object is not found.
		$found = false;

		// If either $cache_db, or $cas_token is set, must hit Memcached and bypass runtime cache.
		if ( func_num_args() > 6 && ! in_array( $group, $this->no_mc_groups, true ) ) {
			if ( $by_key ) {
				$value = $this->m->getByKey( $server_key, $derived_key, $cache_cb, $cas_token );
			} else {
				$value = $this->m->get( $derived_key, $cache_cb, $cas_token );
			}
		} else {
			if ( isset( $this->cache[ $derived_key ] ) ) {
				$found = true;
				return is_object( $this->cache[ $derived_key ] ) ? clone $this->cache[ $derived_key ] : $this->cache[ $derived_key ];
			} elseif ( in_array( $group, $this->no_mc_groups, true ) ) {
				return false;
			} else {
				if ( $by_key ) {
					$value = $this->m->getByKey( $server_key, $derived_key );
				} else {
					$value = $this->m->get( $derived_key );
				}
			}
		}

		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$this->add_to_internal_cache( $derived_key, $value );
			$found = true;
		}

		return is_object( $value ) ? clone $value : $value;
	}

	/**
	 * Retrieves object from cache from specified server.
	 *
	 * Gets an object from cache based on $key and $group, and $server_key. In order to fully support
	 * the $cache_cb and $cas_token parameters, the runtime cache is ignored by this function
	 * if either of those values are set. In that case, the request is made directly
	 * to the memcached server for proper handling of the callback and/or token.
	 * Note that the $cas_token variable cannot be directly passed to the function.
	 * The variable needs to be first defined with a non-null value.
	 *
	 * If using the $cache_cb argument, the new value will always have an expiration
	 * of time of 0 (forever). This is a limitation of the Memcached PECL extension.
	 *
	 * @link https://www.php.net/manual/en/memcached.getbykey.php
	 *
	 * @param string      $server_key The key identifying the server to store the value on.
	 * @param string      $key        The key under which to store the value.
	 * @param string      $group      The group value appended to the $key.
	 * @param bool        $force      Whether or not to force a cache invalidation.
	 * @param null|bool   $found      Variable passed by reference to determine if the value was found or not.
	 * @param null|string $cache_cb   Read-through caching callback.
	 * @param null|float  $cas_token  The variable to store the CAS token in.
	 * @return bool|mixed Cached object value.
	 */
	public function getByKey( $server_key, $key, $group = 'default', $force = false, &$found = null, $cache_cb = null, &$cas_token = null ) {
		/**
		 * Need to be careful how "get" is called. If you send $cache_cb, and $cas_token, it will hit memcached.
		 * Only send those args if they were sent to this function.
		 */
		if ( func_num_args() > 5 ) {
			return $this->get( $key, $group, $force, $found, $server_key, true, $cache_cb, $cas_token );
		} else {
			return $this->get( $key, $group, $force, $found, $server_key, true );
		}
	}

	/**
	 * Requests multiple keys without blocking.
	 *
	 * @link https://www.php.net/manual/en/memcached.getdelayed.php
	 *
	 * @param string|array $keys     Array or string of key(s) to request.
	 * @param string|array $groups   Array or string of group(s) for the key(s).
	 *                               See buildKeys for more on how these are handled.
	 * @param bool         $with_cas Whether to request CAS token values also.
	 * @param null         $value_cb The result callback or null.
	 * @return bool True on success, false on failure.
	 */
	public function getDelayed( $keys, $groups = 'default', $with_cas = false, $value_cb = null ) {
		$derived_keys = $this->buildKeys( $keys, $groups );
		return $this->m->getDelayed( $derived_keys, $with_cas, $value_cb );
	}

	/**
	 * Requests multiple keys without blocking from a specified server.
	 *
	 * @link https://www.php.net/manual/en/memcached.getdelayed.php
	 *
	 * @param string       $server_key The key identifying the server to store the value on.
	 * @param string|array $keys       Array or string of key(s) to request.
	 * @param string|array $groups     Array or string of group(s) for the key(s).
	 *                                 See buildKeys for more on how these are handled.
	 * @param bool         $with_cas   Whether to request CAS token values also.
	 * @param null         $value_cb   The result callback or null.
	 * @return bool True on success, false on failure.
	 */
	public function getDelayedByKey( $server_key, $keys, $groups = 'default', $with_cas = false, $value_cb = null ) {
		$derived_keys = $this->buildKeys( $keys, $groups );
		return $this->m->getDelayedByKey( $server_key, $derived_keys, $with_cas, $value_cb );
	}

	/**
	 * Gets multiple values from memcached in one request.
	 *
	 * See the buildKeys method definition to understand the $keys/$groups parameters.
	 *
	 * @link https://www.php.net/manual/en/memcached.getmulti.php
	 *
	 * @param array        $keys       Array of keys to retrieve.
	 * @param string|array $groups     If string, used for all keys.
	 *                                 If arrays, corresponds with the $keys array.
	 * @param string       $server_key The key identifying the server to store the value on.
	 * @param null|array   $cas_tokens The variable to store the CAS tokens for the found items.
	 * @param int          $flags      The flags for the get operation.
	 * @return bool|array The array of found items on success, false on failure.
	 */
	public function getMulti( $keys, $groups = 'default', $server_key = '', &$cas_tokens = null, $flags = null ) {
		$derived_keys = $this->buildKeys( $keys, $groups );

		/**
		 * If either $cas_tokens, or $flags is set, must hit Memcached and bypass runtime cache.
		 * Note that this will purposely ignore no_mc_groups values as they cannot handle CAS tokens
		 * or the special flags; however, if the groups of groups contains a no_mc_group, this is bypassed.
		 */
		if ( func_num_args() > 3 && ! $this->contains_no_mc_group( $groups ) ) {
			if ( ! empty( $server_key ) ) {
				$values = $this->m->getMultiByKey( $server_key, $derived_keys, $cas_tokens, $flags );
			} else {
				$values = $this->m->getMulti( $derived_keys, $cas_tokens, $flags );
			}
		} else {
			$values      = array();
			$need_to_get = array();

			// Pull out values from runtime cache, or mark for retrieval.
			foreach ( $derived_keys as $key ) {
				if ( isset( $this->cache[ $key ] ) ) {
					$values[ $key ] = $this->cache[ $key ];
				} else {
					$need_to_get[ $key ] = $key;
				}
			}

			// Get those keys not found in the runtime cache.
			if ( ! empty( $need_to_get ) ) {
				if ( ! empty( $server_key ) ) {
					$result = $this->m->getMultiByKey( $server_key, array_keys( $need_to_get ) );
				} else {
					$result = $this->m->getMulti( array_keys( $need_to_get ) );
				}
			}

			// Merge with values found in runtime cache.
			if ( isset( $result ) && Memcached::RES_SUCCESS === $this->getResultCode() ) {
				$values = array_merge( $values, $result );
			}

			// If order should be preserved, reorder now.
			if ( ! empty( $need_to_get ) && Memcached::GET_PRESERVE_ORDER === $flags ) {
				$ordered_values = array();

				foreach ( $derived_keys as $key ) {
					if ( isset( $values[ $key ] ) ) {
						$ordered_values[ $key ] = $values[ $key ];
					}
				}

				$values = $ordered_values;
				unset( $ordered_values );
			}
		}

		// Add the values to the runtime cache.
		$this->cache = array_merge( $this->cache, $values );

		return $values;
	}

	/**
	 * Gets multiple values from memcached in one request by specified server key.
	 *
	 * See the buildKeys method definition to understand the $keys/$groups parameters.
	 *
	 * @link https://www.php.net/manual/en/memcached.getmultibykey.php
	 *
	 * @param string       $server_key The key identifying the server to store the value on.
	 * @param array        $keys       Array of keys to retrieve.
	 * @param string|array $groups     If string, used for all keys.
	 *                                 If arrays, corresponds with the $keys array.
	 * @param null|array   $cas_tokens The variable to store the CAS tokens for the found items.
	 * @param int          $flags      The flags for the get operation.
	 * @return bool|array The array of found items on success, false on failure.
	 */
	public function getMultiByKey( $server_key, $keys, $groups = 'default', &$cas_tokens = null, $flags = null ) {
		/**
		 * Need to be careful how "getMulti" is called. If you send $cache_cb, and $cas_token, it will hit memcached.
		 * Only send those args if they were sent to this function.
		 */
		if ( func_num_args() > 3 ) {
			return $this->getMulti( $keys, $groups, $server_key, $cas_tokens, $flags );
		} else {
			return $this->getMulti( $keys, $groups, $server_key );
		}
	}

	/**
	 * Retrieves a Memcached option value.
	 *
	 * @link https://www.php.net/manual/en/memcached.getoption.php
	 *
	 * @param int $option One of the Memcached::OPT_* constants.
	 * @return mixed The value of the requested option on success, false on failure.
	 */
	public function getOption( $option ) {
		return $this->m->getOption( $option );
	}

	/**
	 * Returns the result code of the last option.
	 *
	 * @link https://www.php.net/manual/en/memcached.getresultcode.php
	 *
	 * @return int Result code of the last Memcached operation.
	 */
	public function getResultCode() {
		return $this->m->getResultCode();
	}

	/**
	 * Return the message describing the result of the last operation.
	 *
	 * @link https://www.php.net/manual/en/memcached.getresultmessage.php
	 *
	 * @return string Message describing the result of the last Memcached operation.
	 */
	public function getResultMessage() {
		return $this->m->getResultMessage();
	}

	/**
	 * Gets server information by key.
	 *
	 * @link https://www.php.net/manual/en/memcached.getserverbykey.php
	 *
	 * @param string $server_key The key identifying the server to store the value on.
	 * @return array Array with host, post, and weight on success, false on failure.
	 */
	public function getServerByKey( $server_key ) {
		return $this->m->getServerByKey( $server_key );
	}

	/**
	 * Gets the list of servers in the pool.
	 *
	 * @link https://www.php.net/manual/en/memcached.getserverlist.php
	 *
	 * @return array The list of all servers in the server pool.
	 */
	public function getServerList() {
		return $this->m->getServerList();
	}

	/**
	 * Gets server pool statistics.
	 *
	 * @link https://www.php.net/manual/en/memcached.getstats.php
	 *
	 * @return array Array of server statistics, one entry per server.
	 */
	public function getStats() {
		return $this->m->getStats();
	}

	/**
	 * Gets server pool memcached version information.
	 *
	 * @link https://www.php.net/manual/en/memcached.getversion.php
	 *
	 * @return array Array of server versions, one entry per server.
	 */
	public function getVersion() {
		return $this->m->getVersion();
	}

	/**
	 * Increments a numeric item's value.
	 *
	 * @link https://www.php.net/manual/en/memcached.increment.php
	 *
	 * @param string $key    The key under which to store the value.
	 * @param int    $offset The amount by which to increment the item's value.
	 * @param string $group  The group value appended to the $key.
	 * @return int|bool Item's new value on success, false on failure.
	 */
	public function increment( $key, $offset = 1, $group = 'default' ) {
		$derived_key = $this->buildKey( $key, $group );

		// Increment values in no_mc_groups.
		if ( in_array( $group, $this->no_mc_groups, true ) ) {

			// Only increment if the key already exists and the number is currently 0 or greater (mimics memcached behavior).
			if ( isset( $this->cache[ $derived_key ] ) && $this->cache[ $derived_key ] >= 0 ) {

				// If numeric, add; otherwise, consider it 0 and do nothing.
				if ( is_numeric( $this->cache[ $derived_key ] ) ) {
					$this->cache[ $derived_key ] += (int) $offset;
				} else {
					$this->cache[ $derived_key ] = 0;
				}

				// Returned value cannot be less than 0.
				if ( $this->cache[ $derived_key ] < 0 ) {
					$this->cache[ $derived_key ] = 0;
				}

				return $this->cache[ $derived_key ];
			} else {
				return false;
			}
		}

		$result = $this->m->increment( $derived_key, $offset );

		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$this->add_to_internal_cache( $derived_key, $result );
		}

		return $result;
	}

	/**
	 * Alias for $this->incr().
	 *
	 * Certain plugins expect an "incr" method on the $wp_object_cache object (e.g., Batcache).
	 * Since the original version of this library matched names to the memcached methods,
	 * the "incr" method was missing. Adding this method restores compatibility with plugins
	 * expecting an "incr" method.
	 *
	 * @param string $key    The key under which to store the value.
	 * @param int    $offset The amount by which to increment the item's value.
	 * @param string $group  The group value appended to the $key.
	 * @return int|bool Item's new value on success, false on failure.
	 */
	public function incr( $key, $offset = 1, $group = 'default' ) {
		return $this->increment( $key, $offset, $group );
	}

	/**
	 * Prepends data to an existing item.
	 *
	 * This method should throw an error if it is used with compressed data. This is an expected behavior.
	 * Memcached casts the value to be prepended to the initial value to the type of the initial value.
	 * Be careful as this leads to unexpected behavior at times. For instance, prepending (float) 45.23
	 * to (int) 23 will result in 45, because the value is first combined (45.2323) then cast to "integer"
	 * (the original value), which will be (int) 45. Due to how memcached treats types, the behavior has been
	 * mimicked in the internal cache to produce similar results and improve consistency. It is recommended
	 * that prepends only occur with data of the same type.
	 *
	 * @link https://www.php.net/manual/en/memcached.prepend.php
	 *
	 * @param string $key        The key under which to store the value.
	 * @param string $value      Must be string as prepending mixed values is not well-defined.
	 * @param string $group      The group value prepended to the $key.
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param bool   $by_key     True to store in internal cache by key; false to not store by key.
	 * @return bool True on success, false on failure.
	 */
	public function prepend( $key, $value, $group = 'default', $server_key = '', $by_key = false ) {
		if ( ! is_string( $value ) && ! is_int( $value ) && ! is_float( $value ) ) {
			return false;
		}

		$derived_key = $this->buildKey( $key, $group );

		// If group is a non-Memcached group, prepend to runtime cache value, not Memcached.
		if ( in_array( $group, $this->no_mc_groups, true ) ) {
			if ( ! isset( $this->cache[ $derived_key ] ) ) {
				return false;
			}

			$combined = $this->combine_values( $this->cache[ $derived_key ], $value, 'pre' );
			$this->add_to_internal_cache( $derived_key, $combined );
			return true;
		}

		// Append to Memcached value.
		if ( $by_key ) {
			$result = $this->m->prependByKey( $server_key, $derived_key, $value );
		} else {
			$result = $this->m->prepend( $derived_key, $value );
		}

		// Store in runtime cache if add was successful.
		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$combined = $this->combine_values( $this->cache[ $derived_key ], $value, 'pre' );
			$this->add_to_internal_cache( $derived_key, $combined );
		}

		return $result;
	}

	/**
	 * Appends data to an existing item by server key.
	 *
	 * This method should throw an error if it is used with compressed data. This is an expected behavior.
	 * Memcached casts the value to be prepended to the initial value to the type of the initial value.
	 * Be careful as this leads to unexpected behavior at times. For instance, prepending (float) 45.23
	 * to (int) 23 will result in 45, because the value is first combined (45.2323) then cast to "integer"
	 * (the original value), which will be (int) 45. Due to how memcached treats types, the behavior has been
	 * mimicked in the internal cache to produce similar results and improve consistency. It is recommended
	 * that prepends only occur with data of the same type.
	 *
	 * @link https://www.php.net/manual/en/memcached.prependbykey.php
	 *
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param string $key        The key under which to store the value.
	 * @param string $value      Must be string as prepending mixed values is not well-defined.
	 * @param string $group      The group value prepended to the $key.
	 * @return bool True on success, false on failure.
	 */
	public function prependByKey( $server_key, $key, $value, $group = 'default' ) {
		return $this->prepend( $key, $value, $group, $server_key, true );
	}

	/**
	 * Replaces a value in cache.
	 *
	 * This method is similar to "add"; however, is does not successfully set a value
	 * if the object's key is not already set in cache.
	 *
	 * @link https://www.php.net/manual/en/memcached.replace.php
	 *
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param string $key        The key under which to store the value.
	 * @param mixed  $value      The value to store.
	 * @param string $group      The group value appended to the $key.
	 * @param bool   $by_key     True to store in internal cache by key; false to not store by key.
	 * @param int    $expiration The expiration time, defaults to 0.
	 * @return bool True on success, false on failure.
	 */
	public function replace( $key, $value, $group = 'default', $expiration = 0, $server_key = '', $by_key = false ) {
		$derived_key = $this->buildKey( $key, $group );
		$expiration  = $this->sanitize_expiration( $expiration );

		// If group is a non-Memcached group, save to runtime cache, not Memcached.
		if ( in_array( $group, $this->no_mc_groups, true ) ) {

			// Replace won't save unless the key already exists; mimic this behavior here.
			if ( ! isset( $this->cache[ $derived_key ] ) ) {
				return false;
			}

			$this->cache[ $derived_key ] = $value;
			return true;
		}

		// Save to Memcached.
		if ( $by_key ) {
			$result = $this->m->replaceByKey( $server_key, $derived_key, $value, $expiration );
		} else {
			$result = $this->m->replace( $derived_key, $value, $expiration );
		}

		// Store in runtime cache if add was successful.
		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$this->add_to_internal_cache( $derived_key, $value );
		}

		return $result;
	}

	/**
	 * Replaces a value in cache on a specific server.
	 *
	 * This method is similar to "addByKey"; however, is does not successfully set a value
	 * if the object's key is not already set in cache.
	 *
	 * @link https://www.php.net/manual/en/memcached.addbykey.php
	 *
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param string $key        The key under which to store the value.
	 * @param mixed  $value      The value to store.
	 * @param string $group      The group value appended to the $key.
	 * @param int    $expiration The expiration time, defaults to 0.
	 * @return bool True on success, false on failure.
	 */
	public function replaceByKey( $server_key, $key, $value, $group = 'default', $expiration = 0 ) {
		return $this->replace( $key, $value, $group, $expiration, $server_key, true );
	}

	/**
	 * Sets a value in cache.
	 *
	 * The value is set whether or not this key already exists in memcached.
	 *
	 * @link https://www.php.net/manual/en/memcached.set.php
	 *
	 * @param string $key        The key under which to store the value.
	 * @param mixed  $value      The value to store.
	 * @param string $group      The group value appended to the $key.
	 * @param int    $expiration The expiration time, defaults to 0.
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param bool   $by_key     True to store in internal cache by key; false to not store by key.
	 * @return bool True on success, false on failure.
	 */
	public function set( $key, $value, $group = 'default', $expiration = 0, $server_key = '', $by_key = false ) {
		$derived_key = $this->buildKey( $key, $group );
		$expiration  = $this->sanitize_expiration( $expiration );

		// If group is a non-Memcached group, save to runtime cache, not Memcached.
		if ( in_array( $group, $this->no_mc_groups, true ) ) {
			$this->add_to_internal_cache( $derived_key, $value );
			return true;
		}

		// Save to Memcached.
		if ( $by_key ) {
			$result = $this->m->setByKey( $server_key, $derived_key, $value, $expiration );
		} else {
			$result = $this->m->set( $derived_key, $value, $expiration );
		}

		// Store in runtime cache if add was successful.
		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$this->add_to_internal_cache( $derived_key, $value );
		}

		return $result;
	}

	/**
	 * Sets a value in cache on a specific server.
	 *
	 * The value is set whether or not this key already exists in memcached.
	 *
	 * @link https://www.php.net/manual/en/memcached.setbykey.php
	 *
	 * @param string $server_key The key identifying the server to store the value on.
	 * @param string $key        The key under which to store the value.
	 * @param mixed  $value      The value to store.
	 * @param string $group      The group value appended to the $key.
	 * @param int    $expiration The expiration time, defaults to 0.
	 * @return bool True on success, false on failure.
	 */
	public function setByKey( $server_key, $key, $value, $group = 'default', $expiration = 0 ) {
		return $this->set( $key, $value, $group, $expiration, $server_key, true );
	}

	/**
	 * Sets multiple values to cache at once.
	 *
	 * By sending an array of $items to this function, all values are saved at once to
	 * memcached, reducing the need for multiple requests to memcached. The $items array
	 * keys and values are what are stored to memcached. The keys in the $items array
	 * are merged with the $groups array/string value via buildKeys to determine the
	 * final key for the object.
	 *
	 * @link https://www.php.net/manual/en/memcached.setmulti.php
	 *
	 * @param array        $items      An array of key/value pairs to store on the server.
	 * @param string|array $groups     Group(s) to merge with key(s) in $items.
	 * @param int          $expiration The expiration time, defaults to 0.
	 * @param string       $server_key The key identifying the server to store the value on.
	 * @param bool         $by_key     True to store in internal cache by key; false to not store by key.
	 * @return bool True on success, false on failure.
	 */
	public function setMulti( $items, $groups = 'default', $expiration = 0, $server_key = '', $by_key = false ) {
		// Build final keys and replace $items keys with the new keys.
		$derived_keys  = $this->buildKeys( array_keys( $items ), $groups );
		$expiration    = $this->sanitize_expiration( $expiration );
		$derived_items = array_combine( $derived_keys, $items );

		// Do not add to memcached if in no_mc_groups.
		foreach ( $derived_items as $derived_key => $value ) {

			// Get the individual item's group.
			$key_pieces = explode( ':', $derived_key );

			// If group is a non-Memcached group, save to runtime cache, not Memcached.
			if ( in_array( $key_pieces[1], $this->no_mc_groups, true ) ) {
				$this->add_to_internal_cache( $derived_key, $value );
				unset( $derived_items[ $derived_key ] );
			}
		}

		// Save to memcached.
		if ( $by_key ) {
			$result = $this->m->setMultiByKey( $server_key, $derived_items, $expiration );
		} else {
			$result = $this->m->setMulti( $derived_items, $expiration );
		}

		// Store in runtime cache if add was successful.
		if ( Memcached::RES_SUCCESS === $this->getResultCode() ) {
			$this->cache = array_merge( $this->cache, $derived_items );
		}

		return $result;
	}

	/**
	 * Sets multiple values to cache at once on specified server.
	 *
	 * By sending an array of $items to this function, all values are saved at once to
	 * memcached, reducing the need for multiple requests to memcached. The $items array
	 * keys and values are what are stored to memcached. The keys in the $items array
	 * are merged with the $groups array/string value via buildKeys to determine the
	 * final key for the object.
	 *
	 * @link https://www.php.net/manual/en/memcached.setmultibykey.php
	 *
	 * @param string       $server_key  The key identifying the server to store the value on.
	 * @param array        $items       An array of key/value pairs to store on the server.
	 * @param string|array $groups      Group(s) to merge with key(s) in $items.
	 * @param int          $expiration  The expiration time, defaults to 0.
	 * @return bool True on success, false on failure.
	 */
	public function setMultiByKey( $server_key, $items, $groups = 'default', $expiration = 0 ) {
		return $this->setMulti( $items, $groups, $expiration, $server_key, true );
	}

	/**
	 * Sets a Memcached option.
	 *
	 * @link https://www.php.net/manual/en/memcached.setoption.php
	 *
	 * @param int   $option Option name.
	 * @param mixed $value  Option value.
	 * @return bool True on success, false on failure.
	 */
	public function setOption( $option, $value ) {
		return $this->m->setOption( $option, $value );
	}

	/**
	 * Builds a key for the cached object using the blog_id, key, and group values.
	 *
	 * This function is inspired by the original WP Memcached Object cache.
	 *
	 * @author Ryan Boren
	 * @link http://wordpress.org/extend/plugins/memcached/
	 *
	 * @param string $key   The key under which to store the value.
	 * @param string $group The group value appended to the $key.
	 * @return string
	 */
	public function buildKey( $key, $group = 'default' ) {
		if ( empty( $group ) ) {
			$group = 'default';
		}

		if ( false !== array_search( $group, $this->global_groups, true ) ) {
			$prefix = $this->global_prefix;
		} else {
			$prefix = $this->blog_prefix;
		}

		return preg_replace( '/\s+/', '', WP_CACHE_KEY_SALT . "$prefix$group:$key" );
	}

	/**
	 * Creates an array of keys from passed key(s) and group(s).
	 *
	 * This function takes a string or array of key(s) and group(s) and combines them into a single dimensional
	 * array that merges the keys and groups. If the same number of keys and groups exist, the final keys will
	 * append $groups[n] to $keys[n]. If there are more keys than groups and the $groups parameter is an array,
	 * $keys[n] will be combined with $groups[n] until $groups runs out of values. 'default' will be used for remaining
	 * values. If $keys is an array and $groups is a string, all final values will append $groups to $keys[n].
	 * If both values are strings, they will be combined into a single string. Note that if more $groups are received
	 * than $keys, the method will return an empty array. This method is primarily a helper method for methods
	 * that call memcached with an array of keys.
	 *
	 * @param string|array $keys   Key(s) to merge with group(s).
	 * @param string|array $groups Group(s) to merge with key(s).
	 * @return array Array that combines keys and groups into a single set of memcached keys.
	 */
	public function buildKeys( $keys, $groups = 'default' ) {
		$derived_keys = array();

		// If strings sent, convert to arrays for proper handling.
		if ( ! is_array( $groups ) ) {
			$groups = (array) $groups;
		}

		if ( ! is_array( $keys ) ) {
			$keys = (array) $keys;
		}

		// If we have equal numbers of keys and groups, merge $keys[n] and $group[n].
		if ( count( $keys ) === count( $groups ) ) {
			for ( $i = 0; $i < count( $keys ); $i++ ) {
				$derived_keys[] = $this->buildKey( $keys[ $i ], $groups[ $i ] );
			}

			// If more keys are received than groups, merge $keys[n] and $group[n]
			// until no more groups are left; remaining groups are 'default'.
		} elseif ( count( $keys ) > count( $groups ) ) {
			for ( $i = 0; $i < count( $keys ); $i++ ) {
				if ( isset( $groups[ $i ] ) ) {
					$derived_keys[] = $this->buildKey( $keys[ $i ], $groups[ $i ] );
				} elseif ( count( $groups ) === 1 ) {
					$derived_keys[] = $this->buildKey( $keys[ $i ], $groups[0] );
				} else {
					$derived_keys[] = $this->buildKey( $keys[ $i ], 'default' );
				}
			}
		}

		return $derived_keys;
	}

	/**
	 * Ensures that a proper expiration time is set.
	 *
	 * Memcached treats any value over 30 days as a timestamp. If a developer sets the expiration
	 * for greater than 30 days or less than the current timestamp, the timestamp is in the past
	 * and the value isn't cached. This function detects values in that range and corrects them.
	 *
	 * @param string|int $expiration The dirty expiration time.
	 * @return string|int The sanitized expiration time.
	 */
	public function sanitize_expiration( $expiration ) {
		if ( $expiration > $this->thirty_days && $expiration <= $this->now ) {
			$expiration = $expiration + $this->now;
		}

		return $expiration;
	}

	/**
	 * Concatenates two values and casts to type of the first value.
	 *
	 * This is used in append and prepend operations to match how these functions are handled
	 * by memcached. In both cases, whichever value is the original value in the combined value
	 * will dictate the type of the combined value.
	 *
	 * @param mixed  $original  Original value that dictates the combined type.
	 * @param mixed  $pended    Value to combine with original value.
	 * @param string $direction Either 'pre' or 'app'.
	 * @return mixed Combined value casted to the type of the first value.
	 */
	public function combine_values( $original, $pended, $direction ) {
		$type = gettype( $original );

		// Combine the values based on direction of the "pend".
		if ( 'pre' === $direction ) {
			$combined = $pended . $original;
		} else {
			$combined = $original . $pended;
		}

		// Cast type of combined value.
		settype( $combined, $type );

		return $combined;
	}

	/**
	 * Simple wrapper for saving object to the internal cache.
	 *
	 * @param string $derived_key Key to save value under.
	 * @param mixed  $value       Object value.
	 */
	public function add_to_internal_cache( $derived_key, $value ) {
		if ( is_object( $value ) ) {
			$value = clone $value;
		}

		$this->cache[ $derived_key ] = $value;
	}

	/**
	 * Determines if a no_mc_group exists in a group of groups.
	 *
	 * @param mixed $groups The groups to search.
	 * @return bool True if a no_mc_group is present; false if a no_mc_group is not present.
	 */
	public function contains_no_mc_group( $groups ) {
		if ( is_scalar( $groups ) ) {
			return in_array( $groups, $this->no_mc_groups, true );
		}

		if ( ! is_array( $groups ) ) {
			return false;
		}

		foreach ( $groups as $group ) {
			if ( in_array( $group, $this->no_mc_groups, true ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Adds global groups.
	 *
	 * This function comes straight from the original WP Memcached Object cache.
	 *
	 * @author Ryan Boren
	 * @link http://wordpress.org/extend/plugins/memcached/
	 *
	 * @param array $groups Array of groups.
	 * @return void
	 */
	public function add_global_groups( $groups ) {
		if ( ! is_array( $groups ) ) {
			$groups = (array) $groups;
		}

		$this->global_groups = array_merge( $this->global_groups, $groups );
		$this->global_groups = array_unique( $this->global_groups );
	}

	/**
	 * Adds non-persistent groups.
	 *
	 * This function comes straight from the original WP Memcached Object cache.
	 *
	 * @author Ryan Boren
	 * @link http://wordpress.org/extend/plugins/memcached/
	 *
	 * @param array $groups Array of groups.
	 * @return void
	 */
	public function add_non_persistent_groups( $groups ) {
		if ( ! is_array( $groups ) ) {
			$groups = (array) $groups;
		}

		$this->no_mc_groups = array_merge( $this->no_mc_groups, $groups );
		$this->no_mc_groups = array_unique( $this->no_mc_groups );
	}

	/**
	 * Gets a value specifically from the internal, run-time cache, not memcached.
	 *
	 * @param int|string $key   Key value.
	 * @param int|string $group Group that the value belongs to.
	 * @return bool|mixed Value on success, false on failure.
	 */
	public function get_from_runtime_cache( $key, $group ) {
		$derived_key = $this->buildKey( $key, $group );

		if ( isset( $this->cache[ $derived_key ] ) ) {
			return $this->cache[ $derived_key ];
		}

		return false;
	}

	/**
	 * Switches blog prefix, which changes the cache that is accessed.
	 *
	 * @param int $blog_id Blog to switch to.
	 * @return void
	 */
	public function switch_to_blog( $blog_id ) {
		global $table_prefix;
		$blog_id           = (int) $blog_id;
		$this->blog_prefix = ( is_multisite() ? $blog_id : $table_prefix ) . ':';
	}
}
// phpcs:enable