Beginning PHP and MySQL: From Novice to Professional Fourth Edition

Chapter 4. Functions

Computer programming exists in order to automate tasks of all sorts, from mortgage payment calculation to determining a person's daily recommended caloric intake. You'll often find that such tasks are comprised of bits of logic which can be reused elsewhere, not only within the same application but also in many other applications. 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 logic used to validate an e-mail address is quite complex, and therefore it would be ideal to maintain the logic in a single location rather than ...