Returns a positive FrontBase link identifier on success, or an error message on failure.
fbsql_connect() establishes a connection to a FrontBase server. The following defaults are assumed for missing optional parameters: hostname = 'NULL', username = '_SYSTEM' and password = empty password.
If a second call is made to fbsql_connect() with the same arguments, no new link will be established, but instead, the link identifier of the already opened link will be returned.
The link to the server will be closed as soon as the execution of the script ends, unless it's closed earlier by explicitly calling fbsql_close().