Symfony’s authorization system - the stuff related to voters and roles - is awesome. It’s simple, it kicks butt, and it’s one of my favorite things, just behind fresh-baked cookies.
But then there’s that other part: authentication. This is how you login: maybe with a form or via OAuth, like Facebook login. This part is probably the single worst part of Symfony. It’s over-engineered, hard to customize and no fun to work with. [...] This problem was screaming for a solution. If we could make Symfony’s authentication system simple and fun, the whole security system would go from a pain, to a powerful tool.
The library they've created, Guard centralizes the authentication handling into one place (via an interface) and makes the basics of authentication handling simpler. In their tutorial they walk you through the use of Guard as a part of a bundle complete with examples of login form and API token authentication handling. He ends the post with a quick comment about a "secret goal" he has to try to have Guard included in symfony itself.