How to keep a variable in COOKIE or GET query string?

With honor to @Wyck’s link, I managed to add a language variable by adding an action hook to init and set the locale into cookie using PHP’s setcookie() function.

For details, visit: Setting custom cookies in WordPress

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