Redirect http page to https

Just a quick one - would anyone know the correct htaccess code to redirect a register.php page from http to https? When the site isn't on the regi开发者_StackOverflowster.php page it should redirect back to http://sitename.com/register.php.

Many thanks.

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I know very little about .htaccess, but I think this page may be of use: http://www.askapache.com/htaccess/http-https-rewriterule-redirect.html