Unable to point the child theme directory even using get_stylesheet_directory()

The answers to this question state that require_once operates at a file-system level. I would try

include get_stylesheet_directory() . '/inc/_customizer.php';

try to change require_once with include and see if that works. If it does, you can research how to use require_once correctly at your leisure.

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