the very very first thig to do is to learn Object Orientated Programming (if you haven't).. then you might want to start learning the MVC pattern... and then you must decide either you star using frameworks (like cakePHP, Symphony,Zend) or you prefer using CMS (like joomla or wordpress)... on the process you might also want to learn javascript using a framework (mootools, jquery or prototype)...
Edited: i forgot about databases and sql!! wow.. there's a lot to learn!
