PHP foreach引用&

1、加引用，才可以改变原数组的值

$oProducts = [
            ['product_id'=>1, 'count'=>3],
            ['product_id'=>2, 'count'=>3],
            ['product_id'=>3, 'count'=>3],
        ];
        foreach($oProducts as &$p)
        {
            $p['order_id'] = 1;
        }
        return json($oProducts);

[{"product_id":1,"count":3,"order_id":1},{"product_id":2,"count":3,"order_id":1},{"product_id":3,"count":3,"order_id":1}]

2、如果不加引用，不能改变原数组的值

$oProducts = [
            ['product_id'=>1, 'count'=>3],
            ['product_id'=>2, 'count'=>3],
            ['product_id'=>3, 'count'=>3],
        ];
        foreach($oProducts as $p)
        {
            $p['order_id'] = 1;
        }
        return json($oProducts);

输出：

[{"product_id":1,"count":3},{"product_id":2,"count":3},{"product_id":3,"count":3}]

3、添加引用，相当于

$oProducts = [
            ['product_id'=>1, 'count'=>3],
            ['product_id'=>2, 'count'=>3],
            ['product_id'=>3, 'count'=>3],
        ];

        foreach($oProducts as $key=>$p)
        {
            $oProducts[$key]['order_id'] = 1;
        }

        return json($oProducts);

输出：

[{"product_id":1,"count":3,"order_id":1},{"product_id":2,"count":3,"order_id":1},{"product_id":3,"count":3,"order_id":1}]