Symfony is a PHP web application. It is for MVC applications. Symfony is free software and released under the MIT(Massachusetts Institute of Technology) license .
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Symfony provides PHP approach via two classes that allow you to interact with the HTTP request and response in an easier way.
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Incoming requests are interpreted by the routing and passed to controller functions that return Response objects. Each page of your site is defined in a routing configuration file that maps different URLs to different PHP functions.
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First, Symfony2 is a collection of over twenty independent libraries that can be used inside any PHP project. These libraries, called the Symfony2 Components, contain something useful for almost any situation, regardless of how your project is developed.
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you'll build the token blog application using only flat PHP. To begin, create a single page that displays blog entries that have been persisted to the database.
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Symfony2 packages "distributions", which are fully-functional applications that include the Symfony2 core libraries, a selection of useful bundles, a sensible directory structure and some default configuration.
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With one file handling all requests, you can centralize things such as security handling, configuration loading, and routing.
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A route defines the URL (e.g. /about) to your page and specifies a controller (which is a PHP function) that Symfony2 should execute when the URL of an incoming request matches the route path.
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A controller is a PHP function you create that takes information from the HTTP request and constructs and returns an HTTP response (as a Symfony2 Response object).
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Besides the values of the routing placeholders, the controller also has access to the Request object when extending the base Controller class.
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A route is a map from a URL path to a controller. For example, suppose you want to match any URL like /blog/my-post or /blog/all-about-symfony and send it to a controller that can look up and render that blog entry.
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A template is simply a text file that can generate any text-based format (HTML, XML, CSV, LaTeX ...).
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Doctrine is totally decoupled from Symfony and using it is optional. Doctrine ORM, which aims to let you map objects to a relational database (such as MySQL, PostgreSQL or Microsoft SQL).
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