如何为会话cookie生成密钥以及何时需要它？

Question

Excerpt from http://php.about.com/od/advancedphp/ss/php_sessions.htm:

So how will it know it's me? Most sessions set a cookie on your computer to uses as a key... it will look something like this: 350401be75bbb0fafd3d912a1a1d5e54.

My question is, in PHP, how to generate a key (e.g., 350401be75bbb0fafd3d912a1a1d5e54) for a session cookie?

And when do we need such a key? Why not just set $_SESSION['color']='red' in the first page and retrieve in the second page with $_SESSION['color']?

Answer 1

how to generate a key (e.g., 350401be75bbb0fafd3d912a1a1d5e54) for a session cookie?

Just call session_start() for this. A key would be generated automatically

when do we need such a key?

when session starts, to distinguish one user from another

Why not just set $_SESSION['color']='red' in the first page and retrieve in the second page with $_SESSION['color']?

This is the way sessions works. You are encouraged to do it this way. Who says you can't do it?