通过CURL访问页面时PHP会话丢失

I was accessing a page set.php on a server which sets a session value on that server. I could see the value in the session by running another script get.php.

Here is my problem: I run the script set.php from my IP and tried to run get.php through a a cURL script, but I cannot see the value set in the session. While accessing the page through cURL, I cant see the value in the session. Why?