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Chris Bates has been teaching a web programming course for several years to a large and diverse group of students during which he has created and refined the examples and exercises used in the book.

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This book is about implementing websites on servers and on browsers. Rather than concentrate in fine detail upon specific technologies, Chris Bates has provided a comprehensive and accessible introduction to the essentials of web development, covering an ever-expanding field in a single volume. Focusing on immediately useful code rather than theory, this is a how-to book for programmers who need quick answers.

Starting with client-side development using HTML and CSS, and moving on to more complex server-side applications written in open source languages such as Perl and PHP, the new edition of this successful textbook has been substantially revised and updated to include increased coverage of PHP and new sections on database design and configuration, Apache and MySQL. Based on years of successful teaching and taking an insightful, example-led approach, Web Programming is the complete all-in-one introduction to website programming and development, ideal for classroom use or self-study.

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This book is about implementing websites on servers and on browsers. Rather than concentrate in fine detail upon specific technologies, Chris Bates has provided a comprehensive and accessible introduction to the essentials of web development, covering an ever-expanding field in a single volume. Focusing on immediately useful code rather than theory, this is a how-to book for programmers who need quick answers.

Starting with client-side development using HTML and CSS, and moving on to more complex server-side applications written in open source languages such as Perl and PHP, the new edition of this successful textbook has been substantially revised and updated to include increased coverage of PHP and new sections on database design and configuration, Apache and MySQL. Based on years of successful teaching and taking an insightful, example-led approach, Web Programming is the complete all-in-one introduction to website programming and development, ideal for classroom use or self-study.

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Web Programming

John Wiley & Sons

Chapter One

This book is an introduction to some of the basic technologies for creating and processing content on Internet Web sites. It is not meant to be a comprehensive guide to any of the areas covered, there are plenty of those available if you need them, but it should provide enough information for the majority of readers. If you find that you want more information, better tutorials or the comprehensive coverage that so many authors favor nowadays, you are directed to the computing shelves of your nearest bookshop. I have attempted to introduce a number of technologies which when combined make an interesting and user-friendly Web site. Hopefully throughout the text there are enough examples to get you started with each of them.

If you are thinking about creating a Web site then you are probably planning to use a lot of text and some images to make it lively, and possibly a sound clip or two. What about building a dynamic and interactive multimedia extravaganza? Sounds intimidating, doesn't it? There are many complex ways of doing these things which require that you be a fully paid up Geek before you begin. There is also a much simpler approach called dynamic HTML, a mix of standard HTML and simple JavaScript, to help you out. It will significantly reduce the development workload and DHTML is supported by all of the popular browsers. This means that you can create leading-edge Web sites without needing to use things like plug-ins or Java applets.

The Web is no longer just a way of presenting information on a computer screen. Being realistic, it has not been for a number of years now. Many commercial sites include some way of getting information from a browser and back to their server. The usual way of doing this is by writing small programs called scripts which run on the server. The process uses a protocol called the Common Gateway Interface or CGI for short. Does this book cater for CGI developers? You bet it does, but to be realistic if you're going to develop any sort of CGI script then you have to understand at least something about programming. It is not so complicated that it has to be left to the people with computer science degrees and years of experience in the internals of complex programming languages like C++ or ADA, but it is complicated. Having said all of that, with a little bit of patience, plenty of hard work, and some thought, many people can write effective server-side scripts.

Web server scripts can be written in almost any programming language. I've chosen to include two languages: Perl and PHP. Perl is probably not the easiest programming language but people from many different backgrounds pick it up quickly enough if they get the right support. The important thing about Perl is that it is perfectly suited to CGI scripting, although it has lots of other uses too. PHP looks very similar to Perl but with a lot of complex syntax removed. It is a phenomenally popular language with libraries available which cover just about any Web development task you can name. It is possible to argue that PHP is now so widely used that it is the single most important technology in this book. PHP works with any Web server but can be optimized to run with Apache using an extension to that server. The interesting thing about PHP is that its growth has happened almost unnoticed by the wider computing community. It is rarely mentioned in the media, yet it is used by millions of sites around the World. PHP is an underground phenomenon which just cannot be ignored.

Those of you interested in CGI scripting should be able to cope with the HTML and JavaScript in the book. Even if you're new to the field you can soon learn what you need to know. But you may want to add more to your site: collecting data about users, creating tailored Web pages, or accessing databases and file systems. Some of these are relatively trivial tasks, as you'll see later, others are at the complicated end of the programming spectrum. If you're keen to learn and willing to work through the examples and exercises even the hardest of these scripts should not prove too difficult.

One technology that I cannot ignore is Extensible Markup Language, XML. This is like HTML after a trip to the gym, it's a way of formatting almost any data so that many applications can handle it. And, fortuitously it just happens that many Web browsers can process or display XML files. With XML, data from spreadsheets, reports, databases, or even applications like CAD packages can be displayed on Web sites. It can be amended and stored in a variety of ways. The computer industry has been looking out for something like XML for a long time. In this book I will give you a taste of what it is and how it can be used and show you a few scripts that let you add the power of XML to your Web site.

Chapter 17 gives you the chance to implement a large system based around an imaginary problem. You can cherry-pick the parts that you choose to do: for instance you may not have access to CGI and database facilities. Whichever part(s) you try should give you a feel for what Web development is all about today. And before anyone asks, no, I don't have a sample solution. There are as many correct (and good) Web sites for any customer as there are developers building those sites.

One more thought, don't dive straight into the most complex parts. Each of the main chapters has some exercises to help you learn. Once you have done the learning you will be able to apply your new knowledge, but not before. That is obvious when someone says it, but take a look around the Web: it is a mess of broken links, bad coding, and sites that are permanently under construction. It is better to know what you are doing, take your time over it and produce an exemplary Web site than to rush in and create something quick but dirty. Surveys suggest that Web sites, especially commercial ones, have just one chance to attract surfers. Make the most of that chance and you will get repeat visits. If you are building business sites then repeat visits equal repeat sales. Customer loyalty starts from that first ever download.

1.1 HTML, XML, AND THE WORLD WIDE WEB

What is HTML and what is it for? First of all, the acronym HTML means Hypertext Markup Language. HTML is a method of describing the format of documents which allows them to be viewed on computer screens. HTML documents are displayed by Web browsers, programs which can navigate across networks and display a wide variety of types of information. HTML pages can be developed to be simple text or to be complex multimedia extravaganzas containing sound, moving images, virtual reality, and Java applets. Most Internet Web pages lie somewhere along that continuum, being mostly text but with a few images to add interest and variety.

The Internet is a global phenomenon which can provide documents from servers across the world to browser clients which can be in any location. If documents are to be readily exchanged across such a vast and complex network, some sort of global protocol is required which allows that information to be viewed anywhere.

The global publishing format of the Internet is HTML. It allows authors not only to use text, but also to format that text with headings, lists, and tables, and to include still images, video, and sound within the text. Readers can access pages of information from anywhere in the...