PHP quicksort

<?php
function quickSort($left,$right,$sort_arr = null){
    static $arr;
    if(!empty($sort_arr)){
        $arr = $sort_arr;
    }

    if($left >= $right){
        return;
    }

    $mark_num = $arr[$left];
    $mark_k = $left;
    $i = $left+1;
    $j = $right;

    while($i != $j){
        //左移判断
        while($arr[$j] > $mark_num && $j > $i){
            $j--;
        }

        //右移判断
        while($arr[$i] <= $mark_num && $i < $j){
            $i++;
        }

        $tmp = $arr[$i];
        $arr[$i] = $arr[$j];
        $arr[$j] = $tmp;   
    }

    if($arr[$i] < $mark_num){
        $arr[$mark_k] = $arr[$i];
        $arr[$i] = $mark_num;
    }

    quickSort($left,$i-1);
    quickSort($i+1,$right);
    return $arr;
}

The above introduces the PHP quick sort method, including aspects of the content. I hope it will be helpful to friends who are interested in PHP tutorials.