PHP Object Cloning
by Vincy. Last modified on June 29th, 2022.
Object cloning is creating a copy of an object. An object copy is created by using the clone keyword and the __clone() method cannot be called directly. In PHP, cloning an object is doing a shallow copy and not a deep copy.
Meaning, that the contained objects of the copied objects are not copied. If you wish for a deep copy, then you need to define the __clone() method.
When there is a need that you do not want the outer enclosing object to modify the internal state of the object then the default PHP cloning can be used. I will demonstrate object cloning using an example in this article.
Copy Objects by Assignment
In the below code, I am attempting to copy an object by using the assignment operator. So what happens is, that the instance is just a pointer to the old instance.
We can verify that by updating the values of its properties. When the values of the new instance are updated it gets reflected in the old instance.
So, this type of copy is just a duplicate reference to the original instance. Technically this is not a copy, but it is just assigning the object’s reference to another object.
<?php
class Animals
{
public $name;
public $category;
}
// Creating instance of Animals class
$objAnimals = new Animals();
// setting properties
$objAnimals->name = "Lion";
$objAnimals->category = "Wild Animal";
// Copying object
$objCopied = $objAnimals;
$objCopied->name = "Cat";
$objCopied->category = "Pet Animal";
print_r($objAnimals);
print_r($objCopied);
?>
When we change $objCopied it affects $objAnimals. The output is,
Values of object $objAnimals:
Animals Object
(
[name] => Cat
[category] => Pet Animal
)
Values of Copied object $objCopied:
Animals Object
(
[name] => Cat
[category] => Pet Animal
)
Object Copy by clone
In the below example, we are copying objects by using the PHP clone keyword. PHP’s clone method does a shallow copy and so, any changes made in the cloned object will not affect the original object.
__clone is a magic method in PHP. Magic methods are predefined in PHP and start with “__” (double underscore). They are executed in response to some events in PHP.
<?php
// Creating instance of Animals class
$objAnimals = new Animals();
// Assigning values
$objAnimals->name = "Lion";
$objAnimals->category = "Wild Animal";
// Cloning the original object
$objCloned = clone $objAnimals;
$objCloned->name = "Elephant";
$objCloned->category = "Wild Animal";
print_r($objAnimals);
print_r($objCloned);
?>
Now we can see the difference in the output of this code.
Values of object $objAnimals:
Animals Object
(
[name] => Lion
[category] => Wild Animal
)
Values of Cloned object $objCopied:
Animals Object
(
[name] => Elephant
[category] => Wild Animal
)
Clone with Deep Copy
To perform a deep copy while cloning in PHP, then you can either overwrite the __clone method in the copied object’s class or serialize and unserialize the object as done below.
<?php
function deepClone($object)
{
return unserialize(serialize($object));
}
?>
For more information on cloning in PHP, refer the php.net’s documentation on cloning.
Comments to “PHP Object Cloning”
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Hi, I’m Vincy. I help build websites, grow businesses, big and small. If that is what you want, contact me.
I’m currently available for freelance work.
Thanks a lot Vincy, the concept was explained crystal clearly.
Welcome Rao.
thanks this helped me!
Welcome Stan.
Great example
Thank you Shabir.
Thanks a lot for this clear and concise article
Welcome Gazi. Keep reading and sharing.
Very clearly explained. Good article.
Thank you Agraj.
Excellent tutorial exactly what I was looking for, thanks!
Welcome Jhonny.
Excellent explanation, thank you.
Welcome Harry.