The short answer is no. Most PHP scripts use little or no object-oriented code at all. The object-oriented approach won't help you do things that you couldn't otherwise achieve. The benefits of object-oriented programming lie in the organization of your scripts, their reusability, and their extensibility. The benefits of object-oriented design can be enormous, however, which is one reason why PHP 5 provides extended support for objects.
Even if you decide not to produce object-oriented code, you might need to decipher third-party programs that contain classes. This hour should help you understand such code.