Curl post method like a form do

Hello, I need to create a PHP code that "POST" (method) the username/password to access some URLs. The URLs are a device that is accessible by http://IP or https://IP, I dont have access to write URL's code. When I "POST" the credentials with a php form, the URL accept authentication then redirect browser to index. But, the credentials are displayed in "view source code". So, I tryed to "POST" with php curl. The authentication works fine, and result return the index page of device. But, I got stuck in my php curl. I need go to http://IP/index.php, already authenticated, like the php form do. Can anyone help me? Thanks. -- Renata Dias