AJAX and PHP

9AJAX RSS ReaderIn the last few years, the Web has become much more active than it used to be. Today, we see anexplosion of new sources of information, such as news sites appearing every day (such ashttp://www.digg.com and http://www.newsvine.com), and the growing trend of web life—weblogs (every person seems to have a weblog these days).As a natural reaction to this invasion of information, many systems that allow grouping, filtering,and aggregating this information have appeared. This is implemented in practice through websyndication, which is that form of syndication where parts of a website (such as news, weblogposts, articles, and so on) are made available for other sites or applications to use.In order to be usable by other parties, the data to be shared must be in a generic format that can belaid out in different formats than in the original source, and when it comes to such formats, RSS2.0 and Atom are the most popular choices.Learn more about the history of RSS and Atom in the Wikipedia—the link to the RSS page ishttp://en.wikipedia.org/wiki/RSS_(protocol).In this chapter, we'll analyze the RSS file format, then take a look at Google Reader (Google'sRSS aggregator), and then build our own RSS aggregator web page with AJAX and PHP.Working with RSSRSS is a widely used XML-based standard, used to exchange information between applications onthe Internet. One of the great advantages of XML is that it is plain text, thus easily read by anyapplication. RSS feeds can be viewed as plain text files, but it doesn't make much sense to usethem like that, as they are meant to be read by specialized software that generates web contentbased on their data.While RSS is not the only standard for expressing feeds as XML, we've chosen to use this formatin the case study because it's very widely used. In order to better understand RSS, we need to seewhat lies underneath the name; the RSS document structure, that is.