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$ this-> myObject = clone $ this-> myObject;

I have a question about cloning objects in PHP. I understand that a clone creates a "deep copy" in that a new object is created with its variables, initialized with the values ​​of the corresponding variables in the object from which it was cloned. However, as described here , this means that any referenced variables will reference the same value, likely creating problems.

The book I am reading has the following solution similar to the one above:

class ReferenceClass {
  public $msg = 'Reference Object';
}

class CloneClass {
  public $refObj;

  public function __construct() {
    $this->refObj = new ReferenceClass();
  }

  public function __clone() {
    $this->refObj = clone $this->$refObj;
  }
}

However, try it as best I could, I can't get my head around what's going on with this line:

    $this->refObj = clone $this->$refObj;

Any light anyone can shed will be of immense help.

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1 answer


Good question.

The line you pointed out clones the referenced objects, so avoid the double pointer problem.

Hence, the method _clone

not only clones the object itself, but all the objects to which it refers.



For example, if you had a car object id 1 that had a reference to the engine object id 1, after the clone you would have a new car identified by 2 and a new engine identified by 2. Without the extension _clone

, you would have a car identified by 2 referencing to the engine identified by 1.

Note that the magic clone is only needed for objects with non-primitive types as attributes.

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