$query = mysql_query("SELECT * FROM `uzytkownicy` WHERE `username` = '$username'");

$numrows = mysql_num_rows($query);

if($numrows!=0)
{
	$row = mysql_fetch_array($query)

	$dbusername = $row['username'];
	$dbpassword = $row['password'];
	$admin = $row['tutaj nazwa pola z tabeli'];
}