PHP and Object-Orientated Programming

I have a medium sized project that I'm started in PHP and mySQL. I think an object-orientated approach may be the best to reduce the amount of code. My question is if I'm using PHP should I even try to do it an object-orientated manner. I've seen some posts that say that doing it this way will really slow down PHP and that if you're doing OO you should really do it in a language like Java.