//połączenie z bazą
$con = mysqli_connect("localhost","dbuser","dbpass","dbname");
//zapytanie do bazy
$query = mysqli_query($con, "SELECT * FROM user WHERE discordId = '".$_SESSION['userId']."'");
//wyświetlanie błędów
if (!$query) 
{
	printf("Error: %s\n", mysqli_error($con));
	exit();
}