順列を生成するPHPプログラムを書いてみたよ！

Math_Permutation.class.php

<?php
class Math_Permutation
{
	private $max;                             //3なら[0,1,2,3]〜[3,2,1,0]の組み合わせとなる
	private $arrayRange            = array(); //内部的に使っているだけなので気にしない
	private $arrayResult           = array(); //0:0,1,2,3、1:0,1,3,2…
	private $arrayResult2dim       = array(); //$this->arrayResultを","で分解した二次元配列
	private $arrayResult2dimExpand = array();


	public function __construct($max)
	{
		$this->set_max($max);
	}


	public function set_max($max)
	{
		$this->max                   = $max + 1;
		$this->arrayRange            = array();
		$this->arrayResult           = array();
		$this->arrayRange            = range(0, $max);
		$this->arrayResult2dim       = array();
		$this->arrayResult2dimExpand = array();
	}


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


	public function get_arrayResult2dim()
	{
		if( 1 > count($this->arrayResult2dim) )
		{
			$this->convertArray_1to2();
		}
		return $this->arrayResult2dim;
	}


	public function get_arrayResult2dimExpand($array)
	{
		$keyY;
		$keyX;
		$line;
		$value;


		if( 1 > count($this->arrayResult2dim) )
		{
			$this->convertArray_1to2();
		}


		if( 1 > count($this->arrayResult2dimExpand) )
		{
			foreach($this->arrayResult2dim as $keyY => $line)
			{
				foreach($line as $keyX => $value)
				{
					$line[$keyX] = $array[$value];
				}
				$this->arrayResult2dimExpand[$keyY] = $line;
			}
		}
		return $this->arrayResult2dimExpand;
	}


	public function generate($max = null, $str = '')
	{
		if( is_null($max) ) $max = $this->max;

		$cnt;
		$array	= array();


		if($max == 0)
		{
			$this->arrayResult[] = rtrim($str, ',');
			return;
		}

		for($y = 0, $cnt = count($this->arrayRange); $y < $cnt; $y++)
		{
			$array = array_splice($this->arrayRange, $y, 1);
			$this->generate($max - 1, $str . $array[0] . ',');
			array_splice($this->arrayRange, $y, 0, $array);
		}
	}


	private function convertArray_1to2()
	{
		$key;
		$value;


		foreach($this->arrayResult as $key => $value)
		{
			$this->arrayResult2dim[$key] = explode(',', $value);
		}
	}
}

呼び出し

<?php
require_once('Math_Permutation.class.php');

$array         = array('a', 'b', 'c');
$o_permutation = new Math_Permutation(2);
$o_permutation->generate();

print "<pre>";
print_r( $o_permutation->get_arrayResult() );                 //1
print_r( $o_permutation->get_arrayResult2dim() );             //2
print_r( $o_permutation->get_arrayResult2dimExpand($array) ); //3
print "</pre>";

実行結果1

Array
(
	[0] => 0,1,2
	[1] => 0,2,1
	[2] => 1,0,2
	[3] => 1,2,0
	[4] => 2,0,1
	[5] => 2,1,0
)

実行結果2

Array
(
	[0] => Array
		(
			[0] => 0
			[1] => 1
			[2] => 2
		)
	[1] => Array
		(
			[0] => 0
			[1] => 2
			[2] => 1
		)
	[2] => Array
		(
			[0] => 1
			[1] => 0
			[2] => 2
		)
	[3] => Array
		(
			[0] => 1
			[1] => 2
			[2] => 0
		)
	[4] => Array
		(
			[0] => 2
			[1] => 0
			[2] => 1
		)
	[5] => Array
		(
			[0] => 2
			[1] => 1
			[2] => 0
		)
)

実行結果3

Array
(
	[0] => Array
		(
			[0] => a
			[1] => b
			[2] => c
		)
	[1] => Array
		(
			[0] => a
			[1] => c
			[2] => b
		)
	[2] => Array
		(
			[0] => b
			[1] => a
			[2] => c
		)
	[3] => Array
		(
			[0] => b
			[1] => c
			[2] => a
		)
	[4] => Array
		(
			[0] => c
			[1] => a
			[2] => b
		)
	[5] => Array
		(
			[0] => c
			[1] => b
			[2] => a
		)
)