Programmatically create a post once a day

If you look at the documentation for get_page_by_title, the 3rd argument is $post_type, Default: page. Since you are creating a post, you should pass in post as the post type when calling get_page_by_title, like below:

if( null == get_page_by_title( $title, OBJECT, 'post' ) )

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