wp_ajax function did not call

Finally I’ve found the problem in your code.
You’ve forgotten \ on namespace path.

class OtherClass{

    public function __construct(){
         add_action('wp_ajax_getItemsByAjax', array( '\Namespace\Common\FooClass', 'getItemsByAjax' ) );
    }

}

I hope it will help you.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)