Held: Thursday, 10 April 2014

Back to Outline 09 - Images as Markup: Exploring SVG. On to Outline 11 - Processing (2).

Summary

We start exploring PHP, a server-side scripting language.

Related Pages

• EBoard (Source) (HTML) (PDF)

Overview

• Web services: Client side vs. server side
• PHP - an overview.
• PHP syntax.

Administrivia

• We'll look at some of the things you built.
• Next homework: Do something interesting with PHP.
  • I'd prefer a Web service.
  • But something to run from the command line would be fun, too.
  • Bonus points (such as they are) for incorporating other technologies.

Web Services: Client-Side and Server-Side

• When folks were first thinking about extending the Web beyond simple static pages, there were three basic approaches
  • Embed applications within the Web page (early: Java; later: Flash, Silverlight)
  • Extend Web pages with a scripting language (Javascript)
  • Generate pages dynamically on the server side.
• Certainly, some things have to reside or happen on the client side (e.g., for responsiveness, you don't want to query the server for each page in an animation).
• Other things have to reside on the server side (e.g., you don't want to ship a complete database to the client)
• Given the design of early interactive servers, you could write server-side applications in more-or-less any language
  • You do need output
  • You generally need to be able to query the environment
• Some languages adapted well to server-side programming (e.g., Perl). Some did not (e.g., C).
• Eventually, people developed languages intended primarily for scripting Web sevices.
• Many possible dangers
  • Flaws in scripts or languages can open your system to others
  • Flaws in scripts or languages can damage performance

PHP Overview

• Perhaps the most popular Web scripting language.
• Part of the legendary LAMP stack
  • Linux Workstation
  • Apache Web Server
  • MySQL database
  • PHP
• Idea: Embed scripts within HTML code (maybe even within CSS code)
• At the root of Drupal, Ushahidi, and thousands (hundreds of thousands?) of other Web applications
• Also usable as a scripting language within the terminal
  • And yes, lots of folks do that.

PHP Syntax

• Yet another "kind of like C, kind of like shell scripting" language.
• <?php ... ?>
• Output: print or echo
• Variables start with a dollar sign.
• Arrays use square braces
  • $courses - array ( "CSC151", "CSC195", "CSC207", "CSC295", "TEC154" );
• One cool variable: $_REQUEST
  • Gives you the request from a Web form.
• A nice variant of arrays: Associative arrays
  • Like arrays, but using symbols as indices
• $course[dept] = "CSC"; $course[number] = "195"; $course[name]

Lab

• Build a formatting explorer. Users enter preferences (color, font, size, whatever you think is interesting) an then you reformat the page according to those preferences.
• Choose your own reference or tutorial. I tend to prefer assorted reference pages. For some quick intro, you might use http://www.webmonkey.com/2010/02/php_tutorial_for_beginners/.