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In this tutorial I ‘m going to show you how fun and simple it is to use cookies to bring interactivity to your Web pages ultimately making you an even more sought-after more confident Web designer.

HTTP is a stateless protocol. Meaning that once the client’s browsers finishes a transactions with the Web server the Web server completely looses all recollection of the transaction. This is, of course, a problem for applications such as a shopping cart in which a state must be maintained. We need a way to send information (such as the data from a shopping cart) and be able to access that data again on all other subsequent request to that server. The most common approach is to use sessions via a combination GET and cookies. So what’s a cookie?

Cookies are very small pieces of information (like little “Post-Its” if you will) that server side scripting languages like PHP utilize to store and retrieve information on the client side. Cookies are tied to a path on the server; meaning that only the domain that issued the cookie can have access to this data. All data is stored as a name-value pair. For Windows NT users the most common place to find your cookies is here C:\Documents and Settings\your Stuff\Cookies; you’ll need to replace your Stuff with the name of your own personal directory.

Moving forwards with syntax. Before going any further there are a number of guidelines you’ll want to remember. Note that you have to put the actual cookies code before any HTML tag; including the head, title, body etc. Cookies are bound to their hierarchical structure meaning any attempts to access a cookie from above its own hierarchy would fail, hence it is best to place the cookie in a file located within the root directory. This will allow you to access the cookie from anywhere on the site. Also, cookies will not become visible until the next loading of the page. Another thing I should mention is cookies can’t exceed 4KB. Doing so just confuses the Web server and forces it to generates a fatal error like the one here.

Bad Request

Your browser sent a request that this server could not understand.

Size of a request header field exceeds server limit.

Moreover browser can only accept up to 20 cookies per domain (300 cookies in total) if the maximum number of cookies is met the browser will delete the least recently used.

Here’s the code.

<?php

setcookie(“cookie”, “hello world”);

?>

setcookie is how we define cookies. This function has a number of parameters (bool setcookie ( string name [, string value [, int expire [, string path [, string domain [, bool secure]]]]] )). I wont go over all of them; however I do think it’s important we discuss the first three.

string name.

<?php

setcookie(“cookie”);

?>

The first parameter (name) is a string value; you should name this something relevant.

string value.

<?php

setcookie(“cookies”, “hello world”);

?>

The second parameter (value) is a string value. Pretty self-explanatory, you recall me saying that all data is stored as a name-value pair. Without a value what would be the point anyway?

int expire.

<?php

setcookie(“cookies”, “hello world”, time() + 3600);

?>

The third parameter (expire) is an integer value. We can set this by using the time function (int time ( void )). This returns the current time measured in the number of seconds since the Unix Epoch. Once we know what time it is we simply add to this the number of seconds we want for the cookie to live. If the parameter is set the cookie lives up to this date. This is known as a persistent cookie. On the other hand if no expiration date is set a so-called session cookie is generated. Session cookies work just the same only they expire once the browser is closed. Needless to say the current time is the state pertaining to the clients own time settings (you have no control over that). So if the client has the wrong date this cookie might expire prematurely. In our example we simply take the current time and add 3600 seconds more; that is to say the cookie will expire 1 hour from the current time. Once you get the hang of it you can start getting fancier maybe add a little JavaScript to determent the users actual date setting etc, etc.

On the next loading of this page or any other page on the same directory or sub directories we can access the cookie as follows.

<?php

echo $_COOKIE["cookie"];

?>

Cookies are great for storing simple name-value pairs but how do you store multiple variables. A common approach is to simply treat the cookie as an array; unfortunately this technique just isn’t practical given that each element in a cookie array is treated as one cookie which brings us right back to the 20 cookies per domain only rule.

A better solution is explode (array explode (string separator, string)). This function returns an array by splitting a string on boundaries formed by a string separator. Here’s an example.

<?php

$airplanes = $fuselage.','.$wings.','.$cockpit.','.$fuel.','.$passengers;< /i>

setcookie(“modernMarvels ”, $airplanes, time() + 3600);

?>

The preceding code assigns five variable values to a cookie in the form of a string. Next explode uses a comma (or any other punctual mark as a string separator) to access each value individually converting string to array. Now all that is left is looping through the array.

<?php

$myvars = explode(“,”,$_COOKIE[modernMarvels]);

$foreach($myvars as $value)

{



echo $value;



}

?>

The final thing is how to delete cookies. One way is to send a cookie with the same name setting its value to an empty string. Intuitively the latter replaces the former however the cookie still subsist; hence a better way is to additionally send a cookie with the same name but with an expiration date that is in the past. Think of this like a little terminator sent from the future back in time to kill itself. Cool hu? For example if you want to delete a cookie called “unstoppableCyborg” here’s what you do.

<?php

setcookie(‘unstopableCyborg’, ‘’, time() – 3600);

?>

Well that about wraps it up here. If you wan to see real multiple value cookies in action simply visit our website www.foamerstudios.com and try adding a few Website templates to our favorites list application. Every single template selection you make will be stored on your machine via cookies. To learn more about cookies visit the preliminary specification guide at htt p://wp.netscape.com/newsref/std/cookie_spec.html

About the author:

Dave Collado is a senior design consultant at www.foamerstudios.com. Our studio offers quality website templates, template customization, flash templates, phpnuke themes, phpbb themes, osCommerce templates, SWiSH templates, icon sets, web design tutorials, and many other web design and web hosting services.