Yes its always possible! 😉
But what you really need to do is to evaluate if its worthwhile building your own site from scratch - with all the functionality that you require. Or pick one 'off the shelf' and extend it / customise it to your needs...
It all depends on what you want - I'm betting that using an old the shelf cms would do the trick and will allow you to add more functionality quickly and easily..
Also theres lots of them to choose from!
eZ Publish
Typo3
PHP Content Mgmt System
PhpThatWare
phpWebsite
PHP-Nuke
PostNuke
Mambo
Midgard
XOOPS
e107
Drupal
I've had done sites with Xoops and Mambo and found them both to be good opensource cms systems,