May 6, 2012

PHP dynamic class extending

Question by tim

I know you can extend a class when constructing it like the following:

class b extends a {

But is it possible to dynamically extend classes from the scripts? Such as:

$b = new b($input) extends a;

What I wish to accomplish is to extend the module differnetly wheither it’s used in admin rather than the public pages. I know I can create two different parent classes by the same name and only include one per admin or public. But my question is, is it possible to do it dynamically in PHP?

Answer by Cory Carson

You can’t, but this has been requested for a few years:

You can define the classes within an eval, but it’s more trouble than declaring the class normally.

Answer by Starx

Yes, as cory mentioned, this feature has been requested before. But before that, you can create a workaround. Here is my old school trick for this

Create two separate classes like these:

class a {
class b {
   public $object;

Then, create an extended version too

class bextendeda extends a {

In the constructor method of class b, place few functions which redirects to the extended object if requested.

class b {
    public $object;

    public function __contruct($extend = false) {
        if($extend) $this -> object = new bextendeda(); 
        else $this -> object = $this;

    function __get($prop) {
        return $this-> object -> $prop;

    function __set($prop, $val) {
       $this-> object -> $prop = $val;
    function __call($name, $arguments)
        return call_user_func_array($this -> object, $arguments);


And there you have it, IF you want the extended version just do this

$b = new b(true);

If not

$b = new b();

Enjoy 🙂

Author: Nabin Nepal (Starx)

Hello, I am Nabin Nepal and you can call me Starx. This is my blog where write about my life and my involvements. I am a Software Developer, A Cyclist and a Realist. I hope you will find my blog interesting. Follow me on Google+


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