What does the clone method in php do?

The role of the clone method in php: used for object copying. Object copying is completed through the clone keyword, such as [$copy_of_object = clone $object;]. The __clone() method in an object cannot be called directly.

php clone method is used for object copying

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In most cases, we don't 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 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.

__clone ( void ) : 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 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
        )
)

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