Cookies in a nutshell Cookies are small pieces of information that is stored on computer of your visitors. Each browser handles it differently, but most simply store information in a small text file. Internet Explorer has a special folder, which can be found in your C:Windows or C:WindowsSystem32 folder. You can delete all your cookies, by going to Options and 'Clearing Cookies' or deleting them by hand. I don't recommend this though.

Almost every website uses cookies. If you go to Amazon.com, you will get several cookies. The same goes for CNN.com. Even Google uses cookies! They are extremely useful for (temporarily) storing information. For example, if you have a login system for your visitors, you could save their userid and password (very heavily encrypted!) so they are automatically logged in next time they visit your website.

Or you could remember their last visit, and highlight everything that is new. And that's just beginning.

Using Cookies Using cookies in PHP is extremely easy. In fact, there is nothing to it, because of PHP's inbuilt setcookie() function. Have a look at documentation, and then try following example:

<?php

// Set a cookie // Cookie name: name // Cookie value: Dennis Pallett // Cookie expire: in 24 hours

setcookie ('name', 'Dennis Pallett', time() + (60*60*24)); ?>

If you run code above, then a cookie will be set. That's all. The cookie name and value are pretty obvious. The cookie expire is when cookie expires, or goes away. Simply use time() function and add number of seconds you want to have cookie available to it. In example I added 60*60*24=86400 seconds, or 24 hours.

If you have looked at documentation, you probably noticed there are additional arguments. As documentation says, path is to limit a cookie to a specific path on your web server. This is often used when you run multiple instances of same script in separate directories. You can safely omit this argument when it doesn't matter if cookie is available site-wide.

There is also domain argument. This can be used to limit cookie to a specific sub-domain, e.g. test.example.com. You can also safely ignore this argument, or set it to .example.com (note beginning period, this is essential!).

Finally, there is also secure argument. This argument is only used for cookies that are sent over a secure HTTPS connection (SSL). Just ignore this argument, unless you're working with a secure connection.

One thing that should be mentioned is that cookies must be set, before you display any HTML/text. It's probably best if you turn on output buffering by putting ob_start() at top of your page.

Now that you have set a cookie, you probably want to retrieve value as well. After all, that is whole point of using cookies. Thankfully, as PHP is ever so easy, you can retrieve same way as you retrieve a GET value. See following example to retrieve value of previous example:

<?php echo 'Your name is ' . $_COOKIE['name']; ?>

This should print "Your name is Dennis Pallett". There's nothing more to it. It's just that easy!

If you still want to be able to check those websites in your favourite aggregator, you need to create your own RSS feed for those websites. This can be done automatically with PHP, using a method called screen scrapping. Screen scrapping is usually frowned upon, as it's mostly used to steal content from other websites.

I personally believe that in this case, to automatically generate a RSS feed, screen scrapping is not a bad thing. Now, on to code!

Getting content For this article, we'll use PHPit as an example, despite fact that PHPit already has RSS feeds.

We'll want to generate a RSS feed from content listed on frontpage. The first step in screen scraping is getting complete page. In PHP this can be done very easily, by using implode(file("", "[the url here]")); IF your web host allows it. If you can't use file() you'll have to use a different method of getting page, e.g. using CURL library.

Now that we have content available, we can parse it for content using some regular expressions. The key to screen scraping is looking for patterns that match content, e.g. are all content items wrapped in <div>'s or something else? If you can successfully discover a pattern, then you can use preg_match_all() to get all content items.

For PHPit, pattern that match content is <div class="contentitem">[Content Here]<div>. You can verify this yourself by going to main page of PHPit, and viewing source.

Now that we have a match we can get all content items. The next step is to retrieve individual information, i.e. url, title, author, text. This can be done by using some more regular expression and str_replace() on each content items.

By now we have following code;

<?php
// Get page $url = "http://www.phpit.net/"; $data = implode("", file($url)); 
// Get content items preg_match_all ("/<div class="contentitem">([^`]*?)</div>/", $data, $matches);