int mysql_close(int [link_identifier] );
Returns: true on success, false on error
mysql_close() closes the link to a MySQL database that's associated with the specified link identifier. If the link identifier isn't specified, the last opened link is assumed.
Note that this isn't usually necessary, as non-persistent open links are automatically closed at the end of the script's execution.
mysql_close() will not close persistent links generated by mysql_pconnect().