Possible Duplicate:
To use WordPress for developing a web application?
For instance, I’ve been using WordPress to build websites and online communities for some time. Recently I’ve been wondering if I should try building web applications using WordPress, which may be a bit strange since WordPress is already a web application. I can’t think of any drawbacks thought.
Is it not recommendable to build a web application with a CMS?
Plenty of people build web applications around the likes of Drupal and WordPress, there’s definitely no reason not to.
The main reason that you might not is because conforming to a CMS can mean reducing your flexibility however people do it so chances are, you can too.
Many people choose to go with a Web Application Framework (e.g. Zend Framework or Django) for developing with as it goes half way between a CMS and the pure language – offering some conveniences but not forcing you into a rigid structure.
Django, for example, even has a CMS built into it. It reads your models and builds a CMS around those.