foreach循环使用&(按址传递)出现的问题

在使用foreach引用地址时，一定要在循环结束后使用unset函数将变量销毁。 因为我没销毁变量，导致后面循环的变量一直在覆盖之前的变量。

示例代码

$map = [
    'all' => [
        'id' => 0,
    ],
    'other' => [
        'id' => 1,
    ],
];

$order = [
    [
        ["id" => 1167, "price" => "86400.00", 'supplier_id' => 1],
        ["id" => 1420, "price" => "990.00", 'supplier_id' => 1],
        ["id" => 1488, "price" => "2.00", 'supplier_id' => 1],
        ["id" => 1442, "price" => "150.00", 'supplier_id' => 1],
        ["id" => 1482, "price" => "150000.00", 'supplier_id' => 1],
        ["id" => 1485, "price" => "150000.00", 'supplier_id' => 1],
        ["id" => 1494, "price" => "5000.00", 'supplier_id' => 2],
        ["id" => 1496, "price" => "2700.00", 'supplier_id' => 2],
    ],
    [
        ["id" => 1499, "price" => "2200.00", 'supplier_id' => 3],
        ["id" => 1452, "price" => "6000.00", 'supplier_id' => 3],
        ["id" => 1455, "price" => "5500.00", 'supplier_id' => 3],
        ["id" => 1479, "price" => "110000.00", 'supplier_id' => 3],
        ["id" => 1415, "price" => "1153176.36", 'supplier_id' => 3],
        ["id" => 1416, "price" => "369555.20", 'supplier_id' => 1],
        ["id" => 1417, "price" => "135200.00", 'supplier_id' => 1],
        ["id" => 1448, "price" => "9700.00", 'supplier_id' => 1],
        ["id" => 1466, "price" => "125.50", 'supplier_id' => 2],
        ["id" => 1472, "price" => "4502.00", 'supplier_id' => 2],
        ["id" => 1478, "price" => "4535.00", 'supplier_id' => 2],
        ["id" => 1491, "price" => "3198.00", 'supplier_id' => 2],
    ]
];

foreach ($map as $key_map => $value_map) {
    //区域ID
    $area_id = $value_map['id'];
    $order_list = isset($order[$area_id]) ? $order[$area_id] : [];
    //供应商表
    $supplier_map = [];
    foreach ($order_list as $value) {
        $supplier_id = $value['supplier_id'];

        if (isset($supplier_map[$supplier_id])) {
            $supplier_map[$supplier_id]['price'] += $value['price'];
        } else {
            $supplier_map[$supplier_id] = [
                'price' => $value['price']
            ];
        }

    }

    foreach ($supplier_map as &$value) {
        //执行其他的处理
    }

    $map[$key_map]['list']=$supplier_map;
}

echo json_encode($map);console.log(actor3.name) // 王五

预计结果

{
    "all":{
        "id":0,
        "list":{
            "1":{
                "price":387542
            },
            "2":{
                "price":7700
            }
        }
    },
    "other":{
        "id":1,
        "list":{
            "3":{
                "price":1276876.36
            },
            "1":{
                "price":514455.2
            },
            "2":{
                "price":12360.5
            }
        }
    }
}

实际结果

{
    "all":{
        "id":0,
        "list":{
            "1":{
                "price":387542
            },
            "2":{
                "id":1491,
                "price":"3198.00",
                "supplier_id":2
            }
        }
    },
    "other":{
        "id":1,
        "list":{
            "3":{
                "price":1276876.36
            },
            "1":{
                "price":514455.2
            },
            "2":{
                "price":12360.5
            }
        }
    }
}

产生原因

内层foreach因为$value变量在按址引用使用后，并没有销毁掉，随即进入下一次的外层foreach循环中。

在下一次的循环中，又有foreach使用$value，循环中将子元素直接赋值给$value变量的物理地址，导致每次循环都会将值给覆盖掉，最终导致数组最后一个元素和下一轮的forache最后一个元素是一致的。

解决方法

1. 在按址引用使用后，使用unset()函数进行内存销毁。
2. foreach循环接收子元素的变量取名不重复。

修改后的示例代码

//1、接收变量取名不重复
    foreach ($supplier_map as &$supplier_map_value) {
        //执行其他的处理
    }

//2、使用unset销毁变量
//unset($value);