One of the Zend Framework's strongest drawing cards, as I see it, is its loosely-coupled structure. The name Zend Framework may be a misnomer, in fact, as ZF is more a set of reusable libraries than an actual application framework. I won't go into detail about the advantages of loose coupling, but a recent discussion on the ZF mailing list prompted me to investigate just how loosely coupled the framework is.

He's created a few graphs to show the extent of the coupling - a directed graph, the density of it and example code showing deep and shallow coupling. Here's his results.

I installed PHP 5.2 on one of my testing servers today and a couple of bits of code that previously worked fine in version 5.1.6 threw fatal errors in the new version. The error message was "Nesting level too deep - recursive dependency?" and it took a little time to track down the root of the problem. Here's what I'd done wrong.

Basically, his problem was using the "non-strict" evaluation for checking if two objects were equal to each other (== instead of ===). This compares everything about them, down to the properties - even if they're references to other properties inside of the same class (which is where the problem lies).

So, the fix is simple - === instead of == when comparing those objects. You'll be happier for the change.