Session Handling Tasks

As stated earlier, the process of PHP maintaining information from one session to the next for a visitor is
pretty straight forward without lacking in capability. This maintaining of information (getting to know the
end user) is accomplished through session handling tasks.

Starting a Session

It is necessary to tell PHP when to open up its eyes and prepare for the possibility of having to get to know
an end user. This process is accomplished through the function session_start(). This function initializes the
session data or continues the current session that is being passed by a request, such as a GET, POST or a
cookie.

<?php
session_start();
?>

Setting up the Session "Key"

After starting the session process, it is important to identify the "key" by which the user will be
remembered. This key is stored on the end users machine and is called when interacting with the end user
machine with the same function; session_id().

<?php
session_start();
// Calling the session ID of the current visitor
echo 'Old session ID :'.session_id();
// Giving the visitor a new session ID
session_id(md5(rand(1,5000)));
echo 'New session ID: '.session_id();
?>

Replacing the Session "Key"

In the example above, the old session ID is removed and a new session ID is made using the rand function.
This works fine; however, there is a simpler approach to the idea of replacing (or regenerating) a new
session ID. This is accomplished with the session_regenerate_id() function that will replace the current
session id with a new one, while keeping the current session information.

<?php
session_start();
// Calling the session ID of the current visitor
echo 'Old session ID :'.session_id();
// Giving the visitor a new session ID
session_regenerate_id();
echo 'New session ID: '.session_id();
?>

Remembering the Session

When working with sessions, it is important to understand that keeping track of the session is utmost for
this recall to take place. If a session ID is lost, then the information that is associated with it is useless
because the key is lost. Without the key, the session information is wasted space. The way PHP prevents
this important "key" from getting lost, is by giving the developers a tool that is easy to pass on. This tool is
the global constant SID and one way it can be applied is in the following manner:

<?php
session_start();
?>
<a href="nextscript.php?<?php echo SID?>">Click here</a>