<?php class Arr { public static function str_to_arr($str) { $pieces = explode(',', $str); foreach ($pieces as $p) { } } public static function arr_to_str($arr) { $str = ''; if (is_array($arr)) { foreach ($arr as $a) { $str .= $a . ','; } $str = rtrim($str, ','); } return $str; } }