Pass data to another form and get response

I want to pass data (a 16 digit key) to another site which will validate the key and return a response. I want to grab the response and check if it's a valid key on my side so I can do some extra stuff with it.

Is this possible? If not, why can't it be done?

EDIT: Ok here's the process. I am grabbing this key from a user input, which can be accessed by grabbing the POST data. After开发者_如何学运维, the data needs to be sent into another form with 1 input field on another site. Ideally, this will produce a result that I can grab on my end.

Some sample test code to give you an idea of calling a remote site behind the scenes:

$key = $_POST['key']

// Create a curl handle to the remote checking server
$ch = curl_init('http://remoteurl/?key=' . $key); 

// Execute 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); 
// Get the reply back
$reply = curl_exec($ch); 

curl_close($ch); 

// Do stuff with the reply
if ($reply == '...')
  // Save $key?!

Ya, it's possible and there are many ways to accomplish it.

cURL is probably going to be your best bet.

Or you could use sockets and directly connect to the target machine on port 80 and throw an HTTP request with form data on it for ultimate control.

Or you could also do it on the client side with javascript.