Developer Larry Ullman is the director of digital media technology for DMC Insights, a consulting firm that specializes in information technology. He is also the author of several best-selling programming guides, including PHP for the World Wide Web: Visual QuickStart Guide and PHP and MySQL for Dynamic Web Sites: Visual QuickPro Guide. Marc Liyenage is a senior software engineer who's been using the C programming language for over 15 years, first on early home computers and PCs, and in the past 10 years on various UNIX/Linux systems, doing commercial Web application work and large-scale Internet/ISP systems design and implementation.