Implementation of mb_substr function

mb_substr.php

<?php
/**
 * Check if mb_substr function is loaded. In case it is not loaded, we implement it.
 */
if ( !function_exists('mb_substr') ) {
	function mb_substr( $str, $start, $length = null, $encoding = null ) {
        preg_match_all( '/./us', $str, $match );
        $chars = is_null( $length ) ? array_slice( $match[0], $start ) : array_slice( $match[0], $start, $length );
        return implode('', $chars );
    }
}

?>