php object copy

In most cases, we do not need to completely copy an object to obtain its properties. But there is one case where it is really needed: if you have a GTK window object that holds window-related resources. You may want to copy a new window, keeping all the same properties as the original window, but it must be a new object (because if it is not a new object, changes in one window will affect the other window). There is another situation: if object A stores a reference to object B, when you copy object A, and you want the object used in it to be no longer object B but a copy of B, then you must get a copy of object A. . Object copying can be done via the clone keyword (this will call the object's __clone() method if possible). The __clone() method in an object cannot be called directly.

$copy_of_object = clone $object;

When the object is copied, PHP 5 will perform a shallow copy of all properties of the object. All reference properties will still be references to the original variables.

void __clone (void)

When the copy is completed, if the __clone() method is defined, the __clone() method in the newly created object (the object generated by copying) will be called and can be used to modify the value of the attribute ( if necessary).

Copy an object

<?php
    class SubObject
    {
        static $instances = 0;
        public $instance;
        public function __construct() {
            $this->instance = ++self::$instances;
        }
        public function __clone() {
            $this->instance = ++self::$instances;
        }
    }
    class MyCloneable
    {
        public $object1;
        public $object2;
        function __clone()
        {
            // 强制复制一份this->object， 否则仍然指向同一个对象
            $this->object1 = clone $this->object1;
        }
    }
    $obj = new MyCloneable();
    $obj->object1 = new SubObject();
    $obj->object2 = new SubObject();
    $obj2 = clone $obj;
    print("Original Object:\n");
    print_r($obj);
    print("Cloned Object:\n");
    print_r($obj2);
?>

The above routine will output:

Original Object:
MyCloneable Object
(
    [object1] => SubObject Object
        (
            [instance] => 1
        )
    [object2] => SubObject Object
        (
            [instance] => 2
        )
)
Cloned Object:
MyCloneable Object
(
    [object1] => SubObject Object
        (
            [instance] => 3
        )
    [object2] => SubObject Object
        (
            [instance] => 2
        )
)