<?php

$str = "apple pear banana orange";
$str_splode = explode(' ',$str);
print_r(showCombo(array(), $str_splode));

function showCombo($str_arr, $arr){
    $ret = array();
    foreach($arr as $val){
       if(!in_array($val, $str_arr)){
           $temp = $str_arr;
           $temp[] = $val;
           print_r($temp);
           $comb = showCombo($temp, $arr);
           if(count($comb) > 0)
              $ret[] = $comb;
       }
    }
    return $ret;
}
?>

Array
(
    [0] => apple
)
Array
(
    [0] => apple
    [1] => pear
)
Array
(
    [0] => apple
    [1] => pear
    [2] => banana
)
Array
(
    [0] => apple
    [1] => pear
    [2] => banana
    [3] => orange
)
Array
(
    [0] => apple
    [1] => pear
    [2] => orange
)
Array
(
    [0] => apple
    [1] => pear
    [2] => orange
    [3] => banana
)
Array
(
    [0] => apple
    [1] => banana
)
Array
(
    [0] => apple
    [1] => banana
    [2] => pear
)
Array
(
    [0] => apple
    [1] => banana
    [2] => pear
    [3] => orange
)
Array
(
    [0] => apple
    [1] => banana
    [2] => orange
)
Array
(
    [0] => apple
    [1] => banana
    [2] => orange
    [3] => pear
)
Array
(
    [0] => apple
    [1] => orange
)
Array
(
    [0] => apple
    [1] => orange
    [2] => pear
)
Array
(
    [0] => apple
    [1] => orange
    [2] => pear
    [3] => banana
)
Array
(
    [0] => apple
    [1] => orange
    [2] => banana
)
Array
(
    [0] => apple
    [1] => orange
    [2] => banana
    [3] => pear
)
Array
(
    [0] => pear
)
Array
(
    [0] => pear
    [1] => apple
)
Array
(
    [0] => pear
    [1] => apple
    [2] => banana
)
Array
(
    [0] => pear
    [1] => apple
    [2] => banana
    [3] => orange
)
Array
(
    [0] => pear
    [1] => apple
    [2] => orange
)
Array
(
    [0] => pear
    [1] => apple
    [2] => orange
    [3] => banana
)
Array
(
    [0] => pear
    [1] => banana
)
Array
(
    [0] => pear
    [1] => banana
    [2] => apple
)
Array
(
    [0] => pear
    [1] => banana
    [2] => apple
    [3] => orange
)
Array
(
    [0] => pear
    [1] => banana
    [2] => orange
)
Array
(
    [0] => pear
    [1] => banana
    [2] => orange
    [3] => apple
)
Array
(
    [0] => pear
    [1] => orange
)
Array
(
    [0] => pear
    [1] => orange
    [2] => apple
)
Array
(
    [0] => pear
    [1] => orange
    [2] => apple
    [3] => banana
)
Array
(
    [0] => pear
    [1] => orange
    [2] => banana
)
Array
(
    [0] => pear
    [1] => orange
    [2] => banana
    [3] => apple
)
Array
(
    [0] => banana
)
Array
(
    [0] => banana
    [1] => apple
)
Array
(
    [0] => banana
    [1] => apple
    [2] => pear
)
Array
(
    [0] => banana
    [1] => apple
    [2] => pear
    [3] => orange
)
Array
(
    [0] => banana
    [1] => apple
    [2] => orange
)
Array
(
    [0] => banana
    [1] => apple
    [2] => orange
    [3] => pear
)
Array
(
    [0] => banana
    [1] => pear
)
Array
(
    [0] => banana
    [1] => pear
    [2] => apple
)
Array
(
    [0] => banana
    [1] => pear
    [2] => apple
    [3] => orange
)
Array
(
    [0] => banana
    [1] => pear
    [2] => orange
)
Array
(
    [0] => banana
    [1] => pear
    [2] => orange
    [3] => apple
)
Array
(
    [0] => banana
    [1] => orange
)
Array
(
    [0] => banana
    [1] => orange
    [2] => apple
)
Array
(
    [0] => banana
    [1] => orange
    [2] => apple
    [3] => pear
)
Array
(
    [0] => banana
    [1] => orange
    [2] => pear
)
Array
(
    [0] => banana
    [1] => orange
    [2] => pear
    [3] => apple
)
Array
(
    [0] => orange
)
Array
(
    [0] => orange
    [1] => apple
)
Array
(
    [0] => orange
    [1] => apple
    [2] => pear
)
Array
(
    [0] => orange
    [1] => apple
    [2] => pear
    [3] => banana
)
Array
(
    [0] => orange
    [1] => apple
    [2] => banana
)
Array
(
    [0] => orange
    [1] => apple
    [2] => banana
    [3] => pear
)
Array
(
    [0] => orange
    [1] => pear
)
Array
(
    [0] => orange
    [1] => pear
    [2] => apple
)
Array
(
    [0] => orange
    [1] => pear
    [2] => apple
    [3] => banana
)
Array
(
    [0] => orange
    [1] => pear
    [2] => banana
)
Array
(
    [0] => orange
    [1] => pear
    [2] => banana
    [3] => apple
)
Array
(
    [0] => orange
    [1] => banana
)
Array
(
    [0] => orange
    [1] => banana
    [2] => apple
)
Array
(
    [0] => orange
    [1] => banana
    [2] => apple
    [3] => pear
)
Array
(
    [0] => orange
    [1] => banana
    [2] => pear
)
Array
(
    [0] => orange
    [1] => banana
    [2] => pear
    [3] => apple
)
Array
(
)