Ticket #18666: allow-arabic-usernames.php

<?php
/*
Plugin Name: Allow Arabic Usernames
Plugin URI: http://core.trac.wordpress.org/ticket/5918
Description: Allows users to register with Arabic usernames.
Author: Sergey Biryukov
Author URI: http://profiles.wordpress.org/sergeybiryukov/
Version: 0.1
*/ 

function aau_sanitize_user($username, $raw_username, $strict) {
        $username = wp_strip_all_tags( $raw_username );
        $username = remove_accents( $username );
        // Kill octets
        $username = preg_replace( '|%([a-fA-F0-9][a-fA-F0-9])|', '', $username );
        $username = preg_replace( '/&.+?;/', '', $username ); // Kill entities

        // If strict, reduce to ASCII and Arabic characters for max portability.
        if ( $strict )
                $username = preg_replace( '|[^a-z\p{Arabic}0-9 _.\-@]|iu', '', $username );

        $username = trim( $username );
        // Consolidate contiguous whitespace
        $username = preg_replace( '|\s+|', ' ', $username );

        return $username;
}
add_filter('sanitize_user', 'aau_sanitize_user', 10, 3);
?>