Another case of not looking in the manual.
resource mysql_pconnect ( [string server [, string username [, string password]]])
Returns a positive MySQL persistent link identifier on success, or FALSE on error.
mysql_pconnect() establishes a connection to a MySQL server. The following defaults are assumed for missing optional parameters: server = 'localhost:3306', username = name of the user that owns the server process and password = empty password.
the server parameter would be "mydomain.com:port#"
Hope this helps