PHP求给定数组的组合

1、求给定数组的组合

如array('a', 'b', 'c')

结果为

a

b

c

a b

a c

b c

function combination($arr){    if(empty($arr)){        return false;    }    $count = count($arr);    for($i=1; $i<$count; $i++){        combinationResult($arr, 0, $count, $i);    }}function combinationResult($arr, $begin, $end, $number){    static $result = array();    if($number == 0){        $count = count($result);        for($i=0; $i<$count; $i++){            echo $result[$i] . ' ';          }        echo '<br/>';        return true;    }    if($begin == $end){        return false;    }    array_push($result, $arr[$begin]);    combinationResult($arr, $begin+1, $end, $number-1);    array_pop($result);    combinationResult($arr, $begin+1, $end, $number);}$arr = array('a', 'b', 'c', 'd');combination($arr);