Add required_if validation language line.

app/lang/en/validation.php

@@ -52,6 +52,7 @@ return array(
 	"numeric"          => "The :attribute must be a number.",
 	"regex"            => "The :attribute format is invalid.",
 	"required"         => "The :attribute field is required.",
+	"required_if"      => "The :attribute field is required when :other is :value.",
 	"required_with"    => "The :attribute field is required when :values is present.",
 	"required_without" => "The :attribute field is required when :values is not present.",
 	"same"             => "The :attribute and :other must match.",