url_to_postid returns 0

when you are at the post URL, you don’t need to work with referer (which is not reliable moreover) but with $GLOBALS["post"] because you are in the PHP code which generate the page

then you can have the post ID with that :

$post_id = $GLOBALS["post"]->ID;

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