Problem with database!

PDOException: SQLSTATE[HY000] [1045] Access denied for user ''@'localhost' (using password: NO) in /var/www/vhosts/gray-whale-02542.zap.cloud/httpdocs/class/database.php:8
Stack trace:
#0 /var/www/vhosts/gray-whale-02542.zap.cloud/httpdocs/class/database.php(8): PDO->__construct()
#1 /var/www/vhosts/gray-whale-02542.zap.cloud/httpdocs/index.php(7): DataBase->__construct()
#2 {main}