1. Please check your PHP version. It should be lower than version 7.
If this is the case, you should move the script under a subdomain and set a compatible PHP version only for that subdomain.
All PHP versions below 7.0 are acceptable.
To check your PHP version, you can access this link in your browser:
2. Check if you do not have syntax errors in bdvars.php config file and all values are saved between double quotes.
$host = "localhost";
$database = "your_database_name";
$user = "your_database_user";
$password = "your_database_password";