成功回傳TRUE失敗回傳FALSE。
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.
注: mysql_close() will not close persistent links created by mysql_pconnect().
See also: mysql_connect(), and
mysql_pconnect().