I think you are almost there!
The message “unknown mysql host database.ispname.com” tells that that the tunnel php file actually is able to connect to the mysql system, but only the databasename is unknown.
So probably just should just supply your username as a prefix for the database like user_mydbname or something like that . Mine is looking like the pic below. It could also be that your ISP has more (physical) Mysql servers and you should supply a number lik 21″ in “mydb1”.
What is the connection string used by myphpadmin ? Should be the same!
All that information should be available from the “control panel” of your web account.