[Joeri]

I'll give an example: zend_validate uses a proper OO hierarchy, so that for each type of validation (maxlength, digits, ...) there's a distinct validator class, which has to be instantiated prior to being applied to a piece of data. The whole thing is really clean and organized ... and abysmally slow, because on each request you're loading dozens of validator classes. That would have been much faster had it been a simple ugly procedural API with all its code in one file. The per-request overhead of input validation is more important than a 'pure' oo design in my opinion.