问下怎么生成所有的不重复的数组

$str    = 'abc';$res    = Arrangement( $str );print_r($res);function Arrangement($arr = array(), $res = '') {  if(! is_array($arr) ) $arr = str_split($arr);  if(empty($arr)) $array[] = $res;  else foreach($arr AS $k => $v) {    unset($arr[$k]);    foreach( Arrangement($arr, $res . $v) AS $t) $array[] = $t;    $arr[$k]    = $v;  }  return  $array;}

Array(    [0] => abc    [1] => acb    [2] => bca    [3] => bac    [4] => cab    [5] => cba)