PHP: "Declaration of ... should be compatible with that of ..."

Question

I'd like to create an interface for entities that are CRUDable (can be saved and deleted). Here is my abstract class:

abstract class AbstractCrudableEntity extends AbstractEntity
{
    abstract public function doSave();
    abstract public function doDelete();
}

My implementing class needs a couple extra parameters to those methods. Here is the signature of the implementing class:

class Contact extends AbstractCrudableEntity {
    public function doSave(User $user, \UberClientManager $manager);
    public function doDelete(User $user, \UberClientManager $manager);
}

I understand that PHP requires that implementing classes have the same parameters for the methods as the parent class (there are several questions that answer this question: this, for example). So that is not the problem.

However, I recently came across some code in Symfony dealing with authentication tokens. The class UsernamePasswordToken extends AbstractToken, and has a different set of parameters in the __construct() method: AbstractToken::__construct() versus UsernamePasswordToken::__construct().

My question is how is Symfony able to do this? What is the difference between this and my code?

score 8 · Accepted Answer · answered Oct 31 '12 at 12:47

8

Overriding constructors is a special case:

Unlike with other methods, PHP will not generate an E_STRICT level error message when __construct() is overridden with different parameters than the parent __construct() method has.

You can not do that with other methods.

answered Oct 31 '12 at 12:47

Elnur Abdurrakhimov

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Wow, I wonder why the constructor is a special case. It seems like they recognized that this functionality is useful, but for some reason limited it to just the constructor. – theunraveler Oct 31 '12 at 12:51
1

[Welcome to the beautiful world of PHP](http://me.veekun.com/blog/2012/04/09/php-a-fractal-of-bad-design/). ;) – Elnur Abdurrakhimov Oct 31 '12 at 12:52
1

Ugh, it's only a matter of time before someone posts that link in a PHP question. – theunraveler Oct 31 '12 at 12:53
Just the case for that link. It hurts. – sepehr Sep 09 '17 at 14:47

score 0 · Answer 2 · answered Oct 31 '12 at 12:48

0

Your child methods must have the same number of parameters as the abstract methods in an abstract parent class.

The constructor in you example is not abstract--the child is just overriding it.

answered Oct 31 '12 at 12:48

Ray

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This doesn't matter. In fact, I tried declaring the methods in `AbstractCrudableEntity` as not abstract, and still got the error. – theunraveler Oct 31 '12 at 12:51

PHP: "Declaration of ... should be compatible with that of ..."

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