Permutation

gistfile1.php

<?php
class Permutation
{
    public static function instance() { return new self(); }
    public function run(Array $nums, $depth, Array $path = array())
    {
        if (count($nums) < $depth) throw new Exception();
        if ($depth === 0) return array($path);
        $ret = array();
        for ($i = 0; $i < count($nums); $i++) {
            $minus_one = $this->minus_one($nums, $i);
            $ret = array_merge($ret, $this->run($minus_one, $depth - 1, $this->plus_one($path, $nums[$i])));
        }
        return $ret;
    }

    public function minus_one(Array $nums, $index)
    {
        $ret = array();
        for ($i = 0; $i < count($nums); $i++) {
            if ($i === $index) continue;
            $ret[] = $nums[$i];
        }
        return $ret;
    }

    public function plus_one(Array $path, $num)
    {
        $path[] = $num;
        return $path;
    }
}

$result = Permutation::instance()->run(array(1, 2, 3, 4, 5), 3);
var_dump($result);