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How to clone an object in PHP

2 min read
Published on 22nd January 2024

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Cloning objects can be useful for a few reasons:

  • You want to make changes to an object but not affect the original

  • You need multiple instances of a complex object with the same basic state

  • You want to duplicate something that took time and resources to initialize

Instead of creating a new object from scratch and manually setting all its properties, cloning saves time and effort.

PHP Clone Syntax

PHP has a built-in way to clone objects - the clone keyword. Here's the syntax:

$copy = clone $original;

This makes $copy a full duplicate of $original. Any changes made to $copy will not affect $original.

You can also call the __clone() magic method manually:

$copy = $original->__clone();

This does the same thing as using the clone keyword.

Cloning Example

Here's a full object cloning example:

// Original object
class Book {
  public $title;
  public $numPages;

  public function __construct($title, $pages) {
    $this->title = $title;  
    $this->numPages = $pages;
  }
}

// Create an instance
$book1 = new Book("A Tale of Two Cities", 384);

// Clone it
$book2 = clone $book1;

// Change the clone's title
$book2->title = "Oliver Twist";

// Original book is unchanged
echo $book1->title; // A Tale of Two Cities
echo $book2->title; // Oliver Twist

As you can see, cloning allows you to duplicate an object and modify it without impacting the original instance.

When Not to Clone

Cloning objects does have some downsides to consider:

  • Performance overhead - Cloning takes time and memory
  • Complex object graphs - Child objects are shallow copied by default

Just keep these limitations in mind when deciding whether cloning is appropriate.

So in summary, the clone keyword in PHP provides an easy way to duplicate objects. Understanding object cloning helps unlock the full power of object-oriented code reuse.

There are some additional examples and helpful resources on PHP's object cloning page.