在文件夹上使用PHP命名空间

I have PHP classes to handle AJAX calls, through a PHP controller.
There are lots of them, all pretty big.
They are in the classes/Core/internalApi/ directory.

I use a composer.json to handle path :

"autoload": {
  "psr-4": {
    "Core\\": "classes/Core/"
  }
}

I don't want to have tenths of use Core\internalAPI\phpClass in my controller.

I've tried (with no success) all possible combinations of the following :

JSON:

""
"internalAPI\\": "classes/Core/internalAPI"

use:

use [[[\]classes][\]Core][\]internalAPI;

call:

[[[\]classes][\]Core][\]internalAPI\phpClass[\phpClass]::func();

Note that I did not forget to run composer update nor composer dump-autoload
And this is not a problem with non-static methods called statically, or anything like that.

What I would like to do :

Have a namespace for classes/Core/internalAPI
Calling functions with internalAPI\fileName\classname::func()