php - How the Laravel controller method get the parameters? -

i studying laravel controller methods. in controller methods, there parameters, not coming route parameters. example,

public function store(request $request) {     $this->validate($request, [         'title' => 'required|unique|max:255',         'body' => 'required',     ]); } 

how laravel controller method parameters? provided parameter $request? how laravel differentiate route parameters , type of parameters?

what see called dependency injection. before laravel calls store() method, analyses it's signature phps reflection capabilities , resolves parameters type-hint class through ioc container. that's how current request injected automatically.

after parameters resolved, route parameters passed. because type-hinted arguments resolved first doesn't matter whether @ beginning, in middle or @ end of argument list. case matters optional route parameters:

doesn't work:

public function store($foo = 'bar', request $request){ 

works:

public function store(request $request, $foo = 'bar'){