[Creating session/cookie using file_get_contents]

I have two domains - http://domaina.com, http://domainb.com

 

I'm calling domainb.com's url from domaina.com:

 

file_get_contents('http://domainb.com/a.php');

 

 

In http://domainb.com/a.php, I'm trying to creating a session or cookie for domainb.com

 

 

<?php
setcookie("key", "value", time()+3600);
 
session_start();
$_session["key1"] = "value1";
?>

 

 

But this code is not working.

 

Please help in solving this issue.

 

Thank you.