A lot of people asked this and we usually get a lot of answers based on biased users who uses a certain framework that works for them. Well hopefully I beg to differ in defining them since I am not an advocate myself, I just try them.
Most of the people would go recommending their favorite framework that works for them. We would hear a lot of easy to use, short learning curve, small footprint and whole lot of convenience factors that would convince a novice to use the one the responder is using. Personally I won’t recommend any of the framework to a novice, it would skip a lot of techniques that a novice should know first before using a framework.
Why I would not recommend it to a beginner? Well basically I have this principle if you used to build the easy way around it would be tougher to build something complicated in the future. Maybe I am wrong with this principle but for me it would be better to have a deeper foundation in how the whole PHP works than jumping to frameworks since it is the easiest way to build websites. I would still recommend to create simple pages out of PHP core to experience the language then push your limits to more complicated ones, then when you jump to frameworks it would be a lot more easier and you can maximize the full potential of the framework.
Why use a framework? It is convenient and the building of websites is really fast. Plus if you are already an advanced PHP coder you can bend and customize classes of your own in a framework that would create a whole lot of options in building websites. You can build your own process inside the framework a new module for your clients in a more convenient way. Frameworks are also lightweight meaning since it is already optimized fetching information would be faster meaning more productivity to your clients.
If you would choose your framework check the community and support to your framework. Nothing beats a good support. Also a healthy community that would help you building your first web application.