PHP快速排序算法

$arr = [5,3,78,65,23,9,15,22,454,56,54,245,2,77,33,134,56,67];
$newArr = quickSort($arr);
echo json_encode($newArr);
/*
    快速排序
*/
function quickSort($array){
if(!isset($array[1])){
return $array;
}
$mid = $array[0];
$leftArray = array();
$rightArray = array();
foreach ($array as $key => $value) {
if($mid > $value){
$leftArray[] = $value;
}
if($mid < $value){
$rightArray[] = $value;
}
}
$leftArray = quickSort($leftArray);
$leftArray[] = $mid;
$rightArray = quickSort($rightArray);
return array_merge($leftArray,$rightArray);
}