How can I call a PHP function inside a hardcoded shortcode?

You could do it in this way.

echo do_shortcode('[mu-events months="11" startmonth="today" orderby="time" orderas="ASC" sites="' . get_current_site() . '"]'); 

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