Calculate sold goods in multi-dimensional array

sold_goods_report.php

<?php
echo "\n" . '-=-=-=-=-=BEFORE LOOP-=-=-=-=-=-=' . "\n". "\n";
$a = array('product name' => 'gasoline', 'quantity' => 2);
$b = array('product name' => 'oil', 'quantity' => 3);
$order1 = array($a,$b);
$c = array('product name' => 'bottle', 'quantity' => 2);
$d = array('product name' => 'gasoline', 'quantity' => 3);
$e = array('product name' => 'lighter', 'quantity' => 1);
$order2 = array($c,$d,$e);
$f = array('quantity' => 13, 'product name' => 'mask');
$g = array('product name' => 'oil', 'quantity' => 7);
$h = array('quantity' => 2, 'product name' => 'lighter', );
$order3 = array($f,$g,$h);
$orders = array ($order1,$order2,$order3);
print_r($orders);
$single_order_array=array();
$results=array();
echo "\n" . '-=-=-=-=-=LOOP-=-=-=-=-=-=' . "\n". "\n";
foreach ($orders as $key => $order) {
    $single_order_array = (array_column($order, 'quantity', 'product name'));
    print_r($single_order_array);
    foreach ($single_order_array as $product=>$quantity){
        if (array_key_exists($product, $results)){
        $results[$product]+=$quantity;}
        else {$results += array ($product=>$quantity);
        }
    }
    
    echo "\n" . '<<<<BREAK>>>>' . "\n". "\n";
    }
echo "\n" . '-=-=-=-=-=AFTER LOOP-=-=-=-=-=-=' . "\n". "\n";
print_r($results);