It wouldn't. It's not a matter of better or worse. It's the paradigm that's important.
All computer programs aim to solve a problem. You can use Imperative Programming or you can use OOP (among others) to solve this problem. OOP will just change how you structure and organize your application, because it embraces concepts like encapsulation, polymorphism, and inheritance (to name some). These are not generally available in imperative programming, but that doesn't mean imperative is worse. It's just different.
If you are coding PHP, you can use either or. PHP is not a strictly object-oriented language. However, as of PHP5, there is an increased focus on OOP. New additions to the API are almost always Classes now (SPL, DateTime, Internationalization). If you want to use those, you definitely should look into OOP.
