php 按元素值获取最佳元素组合

<?phpfunction getClosest($search, $arr) {   $closest = null;   $keyNow = null;   $keys = null;   $min = min($arr);   if ($search <= 0) return '';   foreach ($arr as $key => $item) {      if ($closest === null || abs($search - $closest) > abs($item - $search)) {         $closest = $item;         $keyNow = $key;      }   }   unset($arr[$keyNow]);   $searchNow = abs($closest - $search);   if ($searchNow !== 0 && !empty($arr) && $searchNow >= $min) {        $keys .= ',' . getClosest($searchNow, $arr);   }   array_push($keys, $keyNow);   $keys .= ',' . $keyNow;   return trim($keys, ',');}$arr = array(        '1001' => 100,        '1002' => 200,        '1007' => 200,        '1003' => 300,        // '1004' => 400,        '1005' => 500,);$sr = 800;echo "=================" . PHP_EOL;$a = getClosest($sr, $arr);echo $a;echo PHP_EOL . "=================" . PHP_EOL;