modify from stackoverflow(I forgot where is it :/)

Permute.php

<?php

class Permute implements Iterator
{

    private $base;
    private $count;
    private $current;

    public function __construct($base)
    {
        $this->base = preg_split('/(?<!^)(?!$)/u', $base);
        $this->count = count($this->base);
        $this->current = reset($this->base);
    }

    public function current()
    {
       return $this->current;
    }

    public function key()
    {
        return null;
    }

    public function next()
    {
        for ($it = mb_strlen($this->current, "UTF-8") - 1; $it >= 0; $it--) {
            $cur = preg_split('/(?<!^)(?!$)/u', $this->current);
            $pos = array_search($cur[$it], $this->base);
            if ($pos < ($this->count - 1)) {
                $this->replace_index($this->current, $it, $this->base[$pos + 1]);
                for ($i = $it + 1; $i < mb_strlen($this->current, "UTF-8"); $i++) {
                    $this->replace_index($this->current, $i, reset($this->base));
                }
                break ;
            }
        }

        if ($it == -1) {
            $this->current = str_repeat(reset($this->base), mb_strlen($this->current, "UTF-8") + 1);
        }
   }

    public function rewind()
    {
        $this->current = reset($this->base);
    }

    public function valid()
    {
        return true;
    }

    private function replace_index(&$str, $index, $char)
    {
        $str = preg_split('/(?<!^)(?!$)/u', $str);
        $new = "";

        foreach ($str as $key => $value) {
            if ($key == $index) {
                $new .= $char;
            } else {
                $new .= $value;
            }
        }

        $str = $new;
    }
}
?>