PHP basics

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 is a cookie?

Cookies are very small pieces of information (like little Post-Its notes 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

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 will 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.

setcookie is how we define cookies. This function has a number of parameters

I wont go over all of them; however I do think it’s important we discuss the first three.

string name.

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

string value.

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.

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.

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…

This function returns an array by splitting a string on boundaries formed by a string separator. Here’s an example.

$airplanes = $fuselage.’,’.$wings.’,’.$cockpit.’,’.$fuel.’,’.$passengers;
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.

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 is what you do.

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 http://wp.netscape.com/newsref/std/cookie_spec.html

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Although most of our companies work is template based design, the end result is always unique and adapts to each client’s individual needs. The process of merging a client’s content and style with our templates creates an opportunity to challenge ourselves and once again put our web design skills to the test. Recently, I found myself in a situation where it was necessary to pass information in the form of GET data from a simple Flash button to a server side scripting language- all without reloading the current page. A client was running several different Flash animated banners ads via XML layer popup, underlining some of her most popular website products and online services. She needed a simple way to track the overall efficiency of her small ad campaign. Specifically, she needed to know which banners were being clicked on and which banners were simply annoying or inconsequential to her client base. She also needed to know which were the most popular browsers accessing these pages.

I’ll try to describe what needed to happen with out getting too techie.

An XML layer popup would pop up, offering the end user with a two options. In option A, one could click on the popup. This would take them to wherever the popup was designed to take them. Option B was for the end user to close the popup, and that would simply hide the XML layer’s visibility property. At first, it sounded easy. However, beyond the obvious functionality of options A and B, each option needed to open, write, and save to an external file all without refreshing the current page. After all, the last thing anyone wants to see after closing a popup is another page pop up.

Nevertheless server side scripting languages, like PHP, require a refresh of the page to pass information. Unlike JavaScript which handles its business on the client side of a client server system via your browser (the client), PHP scripts are server-side because they operate solely on the server; data is sent to via POST or GET The script is then parsed, and the new data is sent back to the browser if necessary.

Here’s the solution. I created the following In-line Frame.

Note that the SRC property is the location of our PHP script, which will be summoned later, to write and save to our external file. Notice our width and height properties are both set to zero.

I still submit the data to my PHP script, from within the flash banner popup with the help of ActionScript’s cool little getURL() function:.

However because the target (main) was loaded inside our little hidden iframe, only the iframe refreshes. The user will not see a window refresh, the scrip will be parsed by PHP and everyone lived happily ever after.

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