How to determine, from plugin script, if active theme has The Post Title

Send an HTTP request to the page and search the response body for </h1>.
See this Gist for an example.

Store the result in an option and delete this option when the user switches the theme (hook into the action switch_theme).

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