Beginning PHP and MySQL: From Novice to Professional, Third Edition

CHAPTER 4Functions

Computer programming exists in order to automate tasks of all sorts, from mortgage payment calculation to determining a person's daily recommended caloric intake. However, as these tasks grow increasingly complex, you'll often find they comprise other often repetitive tasks. For example, an e-commerce application might need to validate an e-mail address on several different pages, such as when a new user registers to use a Web site, when somebody wants to add a product review, or when a visitor signs up for a newsletter. The regular expression used to validate an e-mail address is quite complex, and therefore it would be ideal to maintain it in a single location rather than embed it into numerous pages, particularly if it ...