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Chapter 29. Performing Form Validation > Validating the Field Data Type

Validating the Field Data Type

In this section the form validation gets a bit more specific as you learn how to verify the data type of a field. That is, you learn how to tell if a field contains only letters, numbers, or a combination of both.

Checking for Alphabetic Data

Let's begin by looking at a couple of functions that determine whether a field contains alphabetic characters. Specifically, we want to know whether each character in a field is either a lowercase letter (a to z) or an uppercase letter (A to Z). Listing 29.6 presents a couple of functions that do this.


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