Problems related to php quick sorting

How does php implement fast sorting? Function & nbsp; quick (& amp; $ arr, $ low, $ high) {& nbsp; $ key & nbsp; $ low; & nbsp; for ($ I $ low, $ j $ high; $ I! How does php implement fast sorting?

function quick(&$arr,$low,$high){

    $key = $low;
    
    for($i=$low,$j=$high;$i!=$j;){
    
       for(;$j>$key;){
    
           if($arr[$j]<$arr[$key]){

               list($arr[$j],$arr[$key])=swap($arr[$j],$arr[$key]);     
               $key = $j;
               break;

           }else{

               $j--;

           }
    
       }
    
       for(;$i<$key;){
    
           if($arr[$i]>$arr[$key]){

               list($arr[$i],$arr[$key])=swap($arr[$i],$arr[$key]);     
               $key = $i;
               break;

           }else{

               $i++;

           }
    
       }
    }
 
    if($high>$low){ 

        quick($arr,$low,$key-1); 
        quick($arr,$key+1,$high);

    }

}

$arr = array(7,4,9,1,3,2,6,8,0);
quick($arr,0,8);
print_r($arr);

If it is not recursive, it is normal to run it once (remove the if ($ high> $ low) section ). A recursion won't work. Chrome has been turning around for half a day. it should be infinite recursion. Where is the problem?

Php algorithm express sorting

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