On the Zend Framework
Montoya linked to the Zend Framework.
I’ve used various ZF components in projects before (most significantly, the email, search, and feed modules). The result every time has been either:
1) I had to fix or work around a ton of bugs to make it work. or 2) I eventually replaced it with a different library or my own version because the bugs were too severe.
If you ever browse the source, you’ll see why: it’s absolutely terrible. I’d be embarrassed to take credit for most of that code, and I certainly would never release it and suggest that people develop applications dependent on it.
Avoid the Zend Framework.