Prototype Design Pattern using Php

Let's start by added a php class file we call Prototype.php. PHP has built-in cloning support. We can clone an object without defining any special methods as long as the object has fields of primitive types. Fields containing objects retain their references in a cloned object. Therefore, in some cases, you might want to clone those referenced objects as well to grt a deeper copy. You can do this in a special __clone() method.

class Prototype
{
    public $primitive;
    public $component;
    public $circularReference;

    public function __clone()
    {
        $this->component = clone $this->component;
        $this->circularReference = clone $this->circularReference;
        $this->circularReference->prototype = $this;
    }
}

Let's create another file we call ComponentWithBackReference.php. Note that the constructor won't be executed during cloning. If you have complex logic inside the constructor, you may need to execute it in the __clone method as well. The code for this file is:

class ComponentWithBackReference
{
    public $prototype;
    public function __construct(Prototype $prototype)
    {
        $this->prototype = $prototype;
    }
}

At the top of the index.php file we add a couple of includes to inclued the files we just created.

include_once ('Prototype.php');
include_once ('ComponentWithBackReference.php');

We now add some client code to our index.php file.

function clientCode()
{
    $p1 = new Prototype;
    $p1->primitive = 245;
    $p1->component = new \DateTime;
    $p1->circularReference = new ComponentWithBackReference($p1);

    $p2 = clone $p1;
    if ($p1->primitive === $p2->primitive) {
        echo "Primitive field values have been carried over to a clone. Yay!<br/>";
    } else {
        echo "Primitive field values have not been copied. Booo!<br/>";
    }
    if ($p1->component === $p2->component) {
        echo "Simple component has not been cloned. Booo!<br/>";
    } else {
        echo "Simple component has been cloned. Yay!<br/>";
    }

    if ($p1->circularReference === $p2->circularReference) {
        echo "Component with back reference has not been cloned. Booo!\n";
    } else {
        echo "Component with back reference has been cloned. Yay!\n";
    }

    if ($p1->circularReference->prototype === $p2->circularReference->prototype) {
        echo "Component with back reference is linked to original object. Booo!\n";
    } else {
        echo "Component with back reference is linked to the clone. Yay!\n";
    }
}

add:

clientCode();

to run this piece of code. Our result is:

Primitive field values have been carried over to a clone. Yay!
Simple component has been cloned. Yay!
Component with back reference has been cloned. Yay! Component with back reference is linked to the clone. Yay!

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