Web Database Applications with PHP and MySQL, 2nd Edition

Server-Side Validation with PHP

In this section, we introduce validation on the server using PHP. We show you how to validate numbers including currencies and credit cards, strings including email addresses and Zip Codes, and dates and times. We also show you how to check for mandatory fields, field lengths, and data types. Many of the PHP functions we use—including the regular expression and string functions—are discussed in detail in Chapter 3.

We illustrate many of our examples in this section with a case study of validating customer details. The techniques described here are typical of those that validate a form after the user has submitted data to the server. We show how to extend and integrate this approach further in Chapter 10 so that the batch errors are reported as part of a customer form, and we show a completed customer entry form and validation in Chapter 17.

Mandatory Data

Testing whether mandatory fields have been entered is straightforward, and we have implemented this in our examples in Chapter 8. For example, to test if the user's surname has been entered, the following approach is used:

/// Validate the Surname
if (empty($surname))
  formerror($template, "The surname field cannot be blank.", $errors);

The formerror( ) function outputs the error message as a batch error using a template and is discussed in detail in Chapter 8. For simplicity and compactness in the remainder of our examples in this chapter, we omit the formerror( ) function from code fragments and simply ...