How to add an authorized user to a global variable?

Question

Laravel

Hello. I want to implement api on the server and settled on one problem:
How to make the user id entered into a global variable and then the api makes a selection from the database of this user. If possible through:

protected $cat;
 public function __construct() { 
}
private function sendTest(){
}

Because I have a lot of classes and functions, and this problem stops me. Requests pass between controllers and classes