Warning: Trying to access array offset on null in /volume1/Web/www/foto.php on line 654

Fatal error: Uncaught mysqli_sql_exception: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '' at line 1 in /volume1/Web/www/foto.php:660 Stack trace: #0 /volume1/Web/www/foto.php(660): mysqli_query(Object(mysqli), 'SELECT username...') #1 {main} thrown in /volume1/Web/www/foto.php on line 660