How to autoload a class with a different filename? PHP

I would like to autoload the class, but it was declared inside a different filename like this:

AClass.php

namespace path\to\A;

class AClass {}

class AException extends \Exception {}

      

        
        
        
      

    

BClass.php

namespace path\to\B;

use path\to\A\AClass; // I'm actually after AException inside

class BClass {}

class BException extends AException {}

      

        
        
        
      

    

I'm not interested in loading AClass, but AException. However, the above code is not autoloading AException.