I agree with ankur0101, starting with an MVC framework is a good idea. I work with a team that has been using Zend's MVC framework for a while now, its a good choice.
We actually evaluated about 30 PHP frameworks / CMS combination for a project early last year. I ended up picking Pimcore - best of both worlds with MVC framework and clean CMS. My team has been using Pimcore (pimcore.org) for well over a year now. Its a CMS with lots of very useful preview, data/content editing and tracing tools built in, but also light enough that it doesn't get in your way. Used it on both micro-site and big enterprise websites. You should try it out - download at pimcore.org/download.
The Zend MVC framework and Pimcore are both open-source, so eays to just jump in and try them.