登录后使用cURL将数据POST到URL

I am trying to use PHP/cURL to POST data to a URL where being logged in is required. From the PHP code I can execute the login successfully, but when I do the next POST, the site responds that I am not logged in. Any idea as to how the site determines that the login is no longer active for the second POST? One of the POST options for the login is "Remember me from this machine" which I have set. Here is the partial code:I am trying to use PHP/cURL to POST data to a U