Question

How does Facebook, for instance, “redirect” the user when logging into the site? For example, when you initially log in, you are on http://www.facebook.com, then the URL quickly changes to http://www.facebook.com/login.php, and then, assuming you submitted valid email/password, you are redirected back to http://www.facebook.com with your news feed, etc. Also to note, if your email/password are invalid, you are redirected to http://www.facebook.com/login.php and then stopped there and asked to retry your login. Are they using page redirects to achieve this? and if so, are they doing this in PHP…I would assume. Or are they using .htaccess? or another completely different method that I’m unaware of?

Thanks for your answers!

Answer 1

login.php validates the user info, sets cookies, then redirects. If Facebook really does use PHP, it would be

header("Location: http://facebook.com/");
die();