A lot of advancements have been made in the world of PHP Frameworks in the past few years. A solid content management framework gives you the basis for your own customization tailored to the unique requirements of the client.
Zend Framework is a fully object-oriented framework, and as such, it utilizes a lot of object-oriented (OO) concepts like inheritance and interfaces. This makes most, if not all, of ZF’s components extendable to some point. It allows developers to implement their own special variations of individual components without having to hack into the ZF codebase itself. Being able to customize ZF this way allows you to create functionality that is unique to your project, but because of its object-oriented nature, you’ll be able to use this functionality in other projects as well.