State Management in PHP

 

What's a Session?

In terms of time, a session is the amount of time during which a user visits a site. In the programming world, a session is kind of like a big blob that can hold all sorts of variables and values.

·         This blob has an identification string, such as 940f8b05a40d5119c030c9c7745aead9.

·         This identification string is automatically sent to the user when a session is initiated, in a cookie called PHPSESSID (accessible via $_COOKIE[PHPSESSID]).

·         On the server side, a matching temporary file is created with the same name (940f8b05a40d5119c030c9c7745aead9).

When you attempt to retrieve a session variable, the sequence goes something like this (say you're trying to get the value of $_SESSION[count]):

1.      The PHP parser gets the value of $_COOKIE[PHPSESSID] from the user cookie.

2.      The PHP parser finds a matching temporary session file.

3.      Inside the session file, the PHP parser looks for count and then finds its value (say, 76).

4.      $_SESSION[count] is equal to 76.