Возвращает TRUE в случае успешного завершения, FALSE в случае возникновения ошибки.
mysql_close() closes the connection to the MySQL server that's associated with the specified link identifier. If link_identifier isn't specified, the last opened link is used.
Using mysql_close() isn't usually necessary, as non-persistent open links are automatically closed at the end of the script's execution. See also freeing resources.
Замечание: mysql_close() will not close persistent links created by mysql_pconnect().