In this recent post to his PHPJack blog Richard Thomas compares two frameworks - Solar and the Zend Framework on how they handled models.

Not all frameworks support true models and this is one thing that really sets the Solar Framework apart from a lot of frameworks. So what sets Solar apart? Lets replicate what Zend Framework references on models in Solar.. You can find the ZF Docs Here.

After noting that the Zend Framework doesn't fully support true models, instead opting for creating database obejcts and getters/setters to "model" the database behind it. Solar, on the other hand, has a full model class to extend with the ability to perform validation, set up relationships and an example of how it all can be put to use.