I'm looking for the "best practice" way to achieve a message / notification system. I'm using an OOP-based approach for the script and would like to do something along the lines of this:

if(!$something)
   $messages->add('Something doesn\'t exist!');

The add() method in the messages class looks somewhat like this:

class messages {
   public function add($new) {
      $messages = $THIS_IS_WHAT_IM_LOOKING_FOR; //array

      $messages[] = $new;
      $THIS_IS_WHAT_IM_LOOKING_FOR = $messages;
   }
}

In the end, there is a method in which reads out $messages and returns every message as nicely formatted HTML.

So the questions is - what type of variable should I be using for $THIS_IS_WHAT_IM_LOOKING_FOR?

• I don't want to make this use the database. Querying the db every time just for some messages that occur at runtime and disappear after 5 seconds just seems like overkill.
• Using global constants for this is apparently worst practice, since constants are not meant to be variables that change over time. I don't even know if it would work.
• I don't want to always pass in and return the existing $messages array through the method every time I want to add a new message.
• I even tried using a session var for this, but that is obviously not suited for this purpose at all (it will always be 1 pageload too late).

Any suggestions?

Thanks!