Symfony is a set of PHP Components, a Web Application framework, a Philosophy, and a Community — all working together in harmony.
A controller is the PHP function you write that builds the page. You take the incoming request information and use it to create a Symfony Response object, which can hold HTML content, a JSON string or even a binary file like an image or PDF.
The leading PHP framework to create websites and web applications. Built on top of the Symfony Components.
a framework provides you with the certainty that you are developing an application that is in full compliance with the business rules, that is structured, and that is both maintainable and upgradable. Faster, because it allows developers to save time by re-using generic modules in order to focus on other areas. Without, however, ever being tied to the framework itself.