You will learn how to write PHP code to remotely consume services like Google Maps, Flickr, Amazon, YouTube, MSN Search, Yahoo!, Last.fm, and the Internet UPC Database, not to mention the California Highway Patrol Traffic data! You will also learn about the technologies, data formats, and protocols needed to use these web services and APIs, and some of the freely-available PHP tools for working with them.

You will understand how these technologies work with each other and see how to use this information, in combination with your imagination, to build your own cutting-edge websites.

Chapter 1 provides an overview of mashups: what a mashup is, and why you would want one.

In Chapter 2 we create a basic mashup, and go shopping. We will simply look up products on Amazon.com based on the Universal Product Code (UPC). To do this, we cover two basic web services to get our feet wet — XML-RPC and REST. The Internet UPC database is an XML-RPC-based service, while Amazon uses REST. We will create code to call XML-RPC and REST services. Using PHP’s SAX function, we create an extensible object-oriented parser for XML. The mashup covered in this chapter integrates information taken from Amazon’s E-commerce Service (ECS) with the Internet UPC database.

In Chapter 3, we create a custom search engine using the technology of MSN, and Yahoo! The chapter starts with an introduction to SOAP, the most complex of the web service protocols. SOAP relies heavily on other standards like WSDL and XSD, which are also covered in readable detail. We take a look at a WSDL document and learn how to figure out what web services are available from it, and what types of data are passed. Using PHP 5’s SoapClient extension, we then interact with SOAP servers to grab data. We then finally create our mashup, which gathers web search results sourced from Microsoft Live and Yahoo!

For the mashup in Chapter 4, we use the API from the video repository site YouTube, and the XML feeds from social music site Last.fm. We will take a look at three different XML-based file formats from those two sites: XSPF for song playlists, RSS for publishing frequently updated information, and YouTube’s custom XML format. We will create a mashup that takes the songs in two Last.fm RSS feeds and queries YouTube to retrieve videos for those songs. Rather than creating our own XML-based parsers to parse the three formats, we have used parsers from PEAR, one for each of the three formats. Using these PEAR packages, we create an object-oriented abstraction of these formats, which can be consumed by our mashup application.

In Chapter 5, we screen-scrape from the California Highway Patrol website. The CHP maintains a website of traffic incidents. This site auto-refreshes every minute, ensuring the user gets live data about accidents throughout the state of California. This is very valuable if you are in front of a computer. If you are out and about running errands, it would be fairly useless. However, our mashup will use the web service from 411Sync.com to accept SMS messages from mobile users to deliver these traffic incidents to users.

We’ve thrown almost everything into Chapter 6! In this chapter, we use RDF documents, SPARQL, RAP, Google Maps, Flickr, AJAX, and JSON. We create a geographically-centric way to present pictures from Flickr on Google Maps. We see how to read RDF documents and how to extract data from them using SPARQL and RAP for RDF. This gets us the latitude and longitude of London tube stations. We display them on a Google Map, and retrieve pictures of a selected station from Flickr. Our application needs to communicate with the API servers for which we use AJAX and JSON, which is emerging as a major data format. The biggest pitfall in this AJAX application is race conditions, and we will learn various techniques to overcome these.

To follow along with the projects and use the example code in this book, you will need a web server running PHP 5.0 or higher and Apache 1.3.

All of the examples assume you are running the web server on your local work station, and all development is done locally.

Additionally, two projects have special requirements. In Chapter 5, you will need access to a web server that can be reached externally from the Internet. In Chapter 6, you will need a MySQL server. Again, we assume you are running the MySQL server locally and it is properly configured.

To quickly install PHP, Apache, and MySQL, check out XAMPP (http://www.apachefriends.org/en/xampp.html). XAMPP is a one-step installer for PHP, Apache, and MySQL, among other things.

XAMPP is available for Windows, Linux, and Mac OS X. However, many standard Linux distributions already have PHP, Apache, and MySQL installed. Check your distribution’s documentation on how to activate them. Mac OS X already has Apache and PHP installed by default. You can turn them on by enabling Web Sharing in your Sharing Preferences.

MySQL can be installed as a binary downloaded from MySQL.com (http://dev.mysql.com/downloads/mysql/4.1.html).

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

There are three styles for code. Code words in text are shown as follows: “We can include other contexts through the use of the include directive.”

A block of code will be set as follows:

<?php
  $aDom = new DOMDocument();
  try {
     $aDom->loadHTMLFile('examplehtml.html');
  } catch (Exception $ex) {
     $aDom = false;
  }

When we wish to draw your attention to a particular part of a code block, the relevant lines or items will be made bold:

<param>
  <value><string>Hello, world!</string></value>
</param>

Any command-line input and output is written as follows:

Buttercup:~ root# pear list

Buttercup:~ root# is the shell prompt on the author’s machine.

New terms and important words are introduced in a bold-type font. Words that you see on the screen, in menus or dialog boxes for example, appear in our text like this: “In the search box, enter in your keyword and the region code then press Search.”

Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.