Curl login user to external website

Question

yesterday i asked o complex question about it but noone answer it so i want to ask as simply i can.

I want to login user to site b when he logs in site a. ( i want to somekind sso wordpress->lms platform)

im trying to do it with cURL and i use code like this:

$username="..."; 
$password="..."; 
$url="..."; 
$cookie="cookie.txt"; 

$postdata = "login=".$username."&password=".$password; 
$ch = curl_init(); 
curl_setopt ($ch, CURLOPT_URL, $url); 
curl_setopt ($ch, CURLOPT_SSL_VERIFYPEER, FALSE); 
curl_setopt ($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.6) Gecko/20070725 Firefox/2.0.0.6"); 
curl_setopt ($ch, CURLOPT_TIMEOUT, 60); 
curl_setopt ($ch, CURLOPT_FOLLOWLOCATION, 1); 
curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt ($ch, CURLOPT_COOKIEJAR, $cookie); 
curl_setopt ($ch, CURLOPT_REFERER, $url); 
curl_setopt ($ch, CURLOPT_POSTFIELDS, $postdata); 
curl_setopt ($ch, CURLOPT_POST, 1); 
$result = curl_exec ($ch); 

echo $result;  
curl_close($ch);

This script works fine but i have 2 issues: - script redirect me to a siteB and log me in but when i click on some link in siteb i get info im not loged in ( i fink that cURL is loging in the server not user). I guess here i need to read cookie from txt file and add it to user browser ?

• i need to do it in background. So user is not redirected to site b after login on site A. (is curl a good option to do it?)

If anyone was doing something similar please point me in a right direction becouse im stuck on this for 2 days ;(

Here is a link to my previous answer where i explained this case in details:

Wordpress SSO with Chamilo LMS - log in to chamilo in background

Answer 1

You can't set a cookie on behalf of another person for a different domain using a non-browser plugin.

Think about it for a bit... you go to a website and they log you into your bank account w/o showing you that they've done so... how would you feel? Browser security makes that extremely difficult on purpose.