mssql_close() closes the link to a MS SQL Server database that's associated with the specified link identifier. If the link identifier isn't specified, the last opened link is assumed.
如果成功则返回 TRUE，失败则返回 FALSE。
Note that this isn't usually necessary, as non-persistent open links are automatically closed at the end of the script's execution.
mssql_close() will not close persistent links generated by mssql_pconnect().
See also mssql_connect(), and mssql_pconnect().