Umm anyone of you know whats going on with users getting this error?

Lord_Yggdrasill

Well I have a factory structure for generating different types of users, which are classified into categories of Member and Guest. The two categories have their corresponding subcategories, which gives a good rationale to adopt an abstract factory pattern. The problem is that, well, some users of my script are getting errors I am not able to re-produce on my own server. I wonder why it happens... Heres the code structure:

interface Factory{
    public function produce();
    public function massproduce();
}

abstract class UserFactory implements Factory{
    abstract public function produce();
    abstract public function massproduce();

public static function logincheck(){
    // check if a user has logged in by evaluating his/her cookies and sessions
}
}

class MemberFactory extends UserFactory{
     public function produce(){
          // code for generating various of user objects such as member, admin, mod and so on based on userid stored in cookies
     }

public function massproduce(){

}
}

class VisitorFactory extends UserFactory{
     public function produce(){
         // code for generating various user objects such as guest, spider and so on based on IP.
     }

 public function massproduce(){

 }
}

The only issue I see is that the abstract class implements an interface and declares the abstract methods in interface as abstract in itself. It never causes any error for my server running PHP 5.3.18, but users of my script are getting errors like this:

Can't inherit abstract function Factory:: produce() (previously declared abstract in UserFactory)

I was wondering though, is this because of these users having PHP 5.2 or older version of PHP? Or is my server just being weird not able to detecting an error that should be discovered a long time ago?

Weedpacket

Lord Yggdrasill wrote:
The only issue I see is that the abstract class implements an interface and declares the abstract methods in interface as abstract in itself.

Well, why are you doing this? 🙂

But FYI: https://bugs.php.net/bug.php?id=43200

Weedpacket

Lord Yggdrasill wrote:
The only issue I see is that the abstract class implements an interface and declares the abstract methods in interface as abstract in itself.

Well, why are you doing this? 🙂

But FYI: https://bugs.php.net/bug.php?id=43200

Fixed in 5.4.0 and 5.3.9 (www.php.net/ChangeLog-5.php#5.3.9)

Lord_Yggdrasill

I see, then its a glitch with PHP? Guess I will just have to tell users of my script to upgrade PHP lol. But are you saying that what I am doing is actually a bad practice?

johanafm

I don't know what the word on programmer's street is... but my take on this is: not really

It may seem redundant having both an abstract class which declares abstract functions a() and b(), when those in turn are interface functions - from the user's point of view. If any class is to be extending the abstract, it will obviously have to define both a() and b() (or remain abstract itself). Thus, it will be impossible to create a child class without both a() and b(), even without the interface.

However, the interface is there to make sure you (not your users) don't miss defining certain things, just as is the case with an abstract classs (disregarding the obvious differences). So if you have a whole lot of pattern interfaces for example, it does seem natural to implement the factory interface to be certain that you set it up the way it's supposed to be. And yes, I do believe they were correct in addressing this as a bug.

However, if code breaks for your users, all you really need to do in the end, when your abstract class is all done and works as it should, is to drop "implements Factory" and let the users work with that. An inconvinience perhaps, but while it's good to have users with upgraded PHP versions, I wouldn't recommend forcing them to adopt new versions too quickly either. Where I work we usually roll out new version over a couple of weeks, starting in devlopment, then test and finally production. And sometimes we don't get around to upgrading straight away. If we are working to get a lot of new code into production, then we usually hold off with changes to the environment, which means we may not get a new PHP version into test until a month or two after it was released.