Warning: mysqli::__construct(): php_network_getaddresses: getaddrinfo for db failed: Name or service not known in /var/www/html/db_connect.php on line 7

Fatal error: Uncaught mysqli_sql_exception: php_network_getaddresses: getaddrinfo for db failed: Name or service not known in /var/www/html/db_connect.php:7 Stack trace: #0 /var/www/html/db_connect.php(7): mysqli->__construct() #1 /var/www/html/register.php(5): require_once('...') #2 {main} thrown in /var/www/html/db_connect.php on line 7