Contributed by Alexander M. Turek
in #47916
and #47943.

In your Symfony applications you probably have a configuration similar to the
following:

# config/routes.yaml
controllers:
resource: ../src/Controller/
type: attribute

This tells Symfony to look for all PHP files defined in that directory and load
the routes defined as PHP attributes in the classes of those files. Internally,
this uses AnnotationDirectoryLoader and AnnotationFileLoader to find the
route annotations.
More specifically, AnnotationDirectoryLoader finds all PHP files recursively
and AnnotationFileLoader inspects their contents, using PHP token_get_all()
function, to get the full class name for the first class found in the file.
The entire process is cached, so it only impacts performance the first time.
However, since all modern PHP projects use PSR-4 class autoloading, all this
is unnecessary. PSR-4 defines the corresponding file path for a given fully
qualified class name (and vice versa), so there's no need to guess which class
defines each file.
In Symfony 6.2, we're introducing a new PSR-4 routing loader, which is similar
to the annotation routing loader, but finds routes faster because it assumes
that your project files follow PSR-4. See Psr4DirectoryLoader code.
The only needed change in your applications is to define the PSR-4 namespace
used by your controller classes:

# config/routes.yaml
controllers:
- resource: ../src/Controller/
+ resource:
+ path: ../src/Controller/
+ namespace: App\Controller
type: attribute

In addition to the YAML configuration shown above, the namespace option is
also supported in XML and PHP configs.

Sponsor the Symfony project.