Returns a positive Sybase link identifier on success, or FALSE on failure.
sybase_connect() establishes a connection to a Sybase server. The servername argument has to be a valid servername that is defined in the 'interfaces' file.
In case a second call is made to sybase_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 sybase_close().