Merge items in an array based on a subkey, such as quantity

arrayMerge.php

<?php
foreach ($items as $item) {

	if (!isset($mergedItems['key']) {
		$mergedItems[$item['key']] = $item;
	} else {
		$mergedItems[$item['key']]['subKey'] += $item['subKey'];
	}
	
}

// reset the array keys to 0, 1, 2, etc..
$mergedItems = array_values($mergedItems);