Web Database Applications with PHP and MySQL, 2nd Edition

Chapter 9. Validation with PHP and JavaScript

Validation is essential to web database applications. In this chapter, we begin by discussing the types of validation that can be implemented in a web database application, and then show you how to validate data at the server using PHP and at the client using JavaScript.

This chapter extends our discussion of validation in PHP. We have already introduced basic security validation and empty field checks in Chapter 6. We continue here by introducing the principles of validation and the practice of validating form variables and values with PHP. We show you how to validate strings, numbers, dates, times, and Internet addresses, and how some of these tasks can be simplified using PEAR packages.

This chapter also introduces client-side JavaScript. We compare it to PHP and show you the basic techniques used in most common applications. We then describe how simple validation can be performed at the client to save network costs and improve responsiveness of an application to the user. We also introduce other simple tasks that can be effectively accomplished with JavaScript.

This chapter is about user data and helping users to meet system requirements. Parse errors, database server failures, debugging code, and other PHP and database server problems are the subject of Chapter 12.

Validation and Error Reporting Principles

There is nothing worse for a user than annoying, overly persistent, inaccurate, or uninformative validation. For example, error messages ...