Get post thumbnail to display favorites

get_post_thumbnail_id() only returns the ID of the thumbnail.
To get the actual thumbnail you could instead use get_the_post_thumbnail()

You can also get the image using it´s ID, but that requires wp_get_attachment_image( get_post_thumbnail_id(), 'full' )

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