Trying to find why allocate memory exceeds 500MB even when there are 2 entries

quickSort_failing.php

<?php
function quickSort($unsortedArray){
    $leftArray = [];
    $rightArray = [];
    $arrayCount = count($unsortedArray);
    
    //considering middle of array
    $pivot = $unsortedArray[(int)floor($arrayCount / 2)];
    
    for($i = 0; $i < $arrayCount ; $i++){
        if($unsortedArray[$i] < $pivot){
            array_push($leftArray,$unsortedArray[$i]);       
        
        }else{
            array_push($rightArray,$unsortedArray[$i]);
        }
    }
    $tempRight =  quickSort($rightArray);
    $sortedRight = array_push($pivot,$tempRight);
    $tempLeft = quickSort($leftArray);
    $sortedLeft = array_push($tempLeft,$sortedRight);
    return array_push($sortedRight,$sortedRight);
}


$unsortedArray = [200,100];
var_dump($unsortedArray);

$sortedArray =  quickSort($unsortedArray);

var_dump($sortedArray);
?>