PHP优化教程之解决嵌套问题

	$orderList = select * from order where xx;
	foreach($orderList as $orderItem) {
		$orderItem->detailList = select * from order_detail where order_id = $orderItem->id;
	}

	$orderList = select * from order where xx;
	$orderId = array_pluck($orderList, 'id'); // Laravel内置数组辅助函数
	$orderDetailList = select * from order_detail where order_id IN $orderId;
	foreach($orderList as $orderItem) {
		$detailListTemp = [];
		foreach($orderDetailList as $orderDetailItem) {
			if ($orderItem->id == $orderDetailItem->order_id) {
				$detailListTemp[] = $orderDetailItem;		
			}
		}
		$orderItem->detailList = $detailListTemp;
	}

	$orderList = select * from order where xx;
	$orderId = array_pluck($orderList, 'id'); // Laravel内置数组辅助函数
	$orderDetailList = select * from order_detail where order_id IN $orderId;

	// 将订单详情转换成以订单ID为索引【方式1】
	$orderDetailList = arrayGroup($orderDetailList, 'order_id');
	// 或：将订单详情转换成以订单ID为索引【方式2:如果为一对一，可以用array_column】
	// $orderList = array_column($orderDetailList, null, 'order_id'); 

	foreach($orderList as $orderItem) {
		$orderItem->detailList = $orderDetailList[$orderItem->id] ?? [];
	}

	// 根据KEY数组分组
	function arrayGroup($list, $key) {
	 $newList = [];
	 foreach ($list as $item) {
	  $newList[$item[$key]][] = $item;
	 }
	 return $newList;
	}