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Sessions and cookies. What are they? Smoking marijuana and eating biscuits? Hell no - in the web development world they are very important functions of interactive design! The difference between sessions and cookies, though, basically revolves around where the variables are stored.  Here's a basic explanation:

Simple Sessions Management
Let’s start with sessions. In short they can be defined as pieces of data recorded by a web script and stored on the server.  They can be programmed to last for a certain amount of time, but are usually erased when the user shuts their browser, although it is required that the function session_start() be called before ANY output is sent to the browser. To be on the safe side, I usually put this function declaration on the first line of code in a web script. The easiest way to create and manage sessions in PHP (4+) is as follows:

<? session_start(); $_SESSION[‘session_name’] = ‘your data’; ?>

You can use this same variable to compare with other strings in IF statements, etc. If for any reason you wish to erase a session before the user shuts their browser, you use session_destroy():

<? session_destroy(‘session_name’); ?>

Let’s write a simple sessions script with two pages.  Put the following code on page 1:

<? session_start(); echo ‘Welcome to our sessions test! Your example username can be pogo!’; $_SESSION[‘username’] = ‘pogo’; echo ‘<a href=”page2.php”>Click here to have a session</a>’; ?>

And this code on page 2:

<? session_start(); echo ‘If all goes well, your username should show as “pogo”.’; $username = $_SESSION[‘username’]; echo ‘Username: ‘.$username; echo ‘Welcome pogo!’; ?>

Of course this script has no user entered data, but that is only one modification away (i.e. by adding an HTML form). I think this example is sufficient enough to demonstrate how sessions work - Yes, its so simple even a monkey could do it, and people say sessions are hard!

Simple Cookie Usage
Now on to cookies (YUM!). Cookies are the basically the same as sessions, except that they are stored locally (on your PC). If you are using M$ Windows then the chances are that they are stored in [windows default folder]\Cookies, although if you have user profiles enabled they will be located in your personal profile’s cookie folder.  They are used the same way as the sessions are above, with SESSION replaced with COOKIE:

<? $_COOKIE[‘cookie_name’] = ‘your data’; $name = $_COOKIE[‘cookie_name’]; echo $name; // this outputs “your data” on your page ?>

You can use the same example script as provided for the sessions tutorial above, replacing “SESSION” with “COOKIE”.

There are more complicated ways of registering cookies which I wont go into because this is a basic tutorial - They have extra attributes that allow you to set the timeout limit, domain, cookie name, data, etc.

I hope you found this tutorial useful!  For more information on sessions go here, and for greater detail on cookies, look over here.   Good luck!

- Tutorial written by Scrowler

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