Failed to connect to MySQL: SQLSTATE[HY000] [2002] No such file or directory

Notice: Undefined variable: conn in /var/www/techguide/index.php on line 77

Fatal error: Uncaught Error: Call to a member function prepare() on null in /var/www/techguide/index.php:77 Stack trace: #0 {main} thrown in /var/www/techguide/index.php on line 77