public static function explode($separator, $data, $number = null, $callback = 'array_push')
    {
        if ($number) {
            $array = explode($separator, $data, $number);
        } else {
            $array = explode($separator, $data);
        }

        if (count($array) < $number) {
            foreach (range(1, $number - count($array)) as $i) {
                $callback($array, null);
            }
        }

        return $array;
    }