i've got a requirement like, after i login then my url ought to be change 'http://' to 'https://'. all of the data tranfer ought to be via SSL. how to achieve that? thanks..

Redirect your user to https:// protocol.

Take a look from php manual: http://www.php.net/manual/en/reserved.variables.server.php#100877

have your login form undergo a https address... also make certain you've installed an SSL certificate in your server first.