When processing queries that return MANY rows, and when you put a limit on the number of rows you fetch from the result set, you should always call this function to close the current result set, because the SQL server may still be pending waiting for other rows to be fetched by your script. When you call this function, the Sybase client in PHP3 will signal to Sybase SQL Server that other pending results can be ignored, and the SQL server connection will return faster to the "waiting command" state, instead of keeping in the "suspend" state, saving much resources on the SQL-Server. In fact, it is a good idea to call this function after all your queries to save up SQL server resources.
Note that when processing SQL batchs with multiple queries, and stored procedure calls that return multiple result sets, there's no provision here to let the server return the next result set. There should be another function like sybase_next_result() to close the current result set, and let the SQL server go on the next SQL statements. Such a function would return a status that indicates if further results are coming or if the query is really terminated.