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Object replication
Usage scenarios:
1. If you have a GTK window object, the object 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).
2. 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 object A a copy of .
Implementation: Through the clone keyword (this will call the object's __clone() method if possible), the __clone() method in the object cannot be called directly.
$copy_of_object = clone $object;
When an 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 copying 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).
Example #1 复制一个对象<?phpclass 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);/* Original Object: MyCloneable Object ( [object1] => SubObject Object ( [instance] => 1 ) [object2] => SubObject Object ( [instance] => 2 ) ) */print("Cloned Object:\n"); print_r($obj2);/* Cloned Object: MyCloneable Object ( [object1] => SubObject Object ( [instance] => 3 ) [object2] => SubObject Object ( [instance] => 2 ) ) */?>
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