fbsql_connect() establishes a connection to a FrontBase server.
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().
The server host name. Defaults to 'NULL'.
The user name for the connection. Defaults to _SYSTEM.
The user name for the connection. Defaults to the empty string.