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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 ) )