Question

I need to implement an observer design pattern in PHP. The problem with the standard SplObserver interface is that its update(SplSubject $subject) method doesn’t support supplying additional arguments which is necessary for me.

Do I have to create my own interface like this?

interface PushObserver {
  public function update($sender, array $pushData);
}

Or is there a more standard way which wouldn’t require users of my class to implement my own interface? I know I am not the only one dealing with this, but I haven’t found a single article about this issue.

Answer 1

I don’t know if it’s really important to you to demand $pushData in your observer, but if it’s only optional you can still implement or extend SplObserver, but make the $pushData optional, it lets you do that:

class PushObserver implements SplObserver {
    public function update (SplSubject $SplSubject, Array $pushData = null) {}
}

Or:

interface PushObserver extends SplObserver {
    public function update (SplSubject $SplSubject, Array $pushData = null);
}