Learning PHP, MySQL, JavaScript, CSS & HTML5, 3rd Edition

Chapter 17. JavaScript and PHP Validation and Error Handling

With your solid foundation in both PHP and JavaScript, it’s time to bring these technologies together to create web forms that are as user-friendly as possible.

We’ll be using PHP to create the forms and JavaScript to perform client-side validation to ensure that the data is as complete and correct as it can be before it is submitted. Final validation of the input will then be made by PHP, which will, if necessary, present the form again to the user for further modification.

In the process, this chapter will cover validation and regular expressions in both JavaScript and PHP.

Validating User Input with JavaScript

JavaScript validation should be considered an assistance more to your users than to your websites because, as I have already stressed many times, you cannot trust any data submitted to your server, even if it has supposedly been validated with JavaScript. This is because hackers can quite easily simulate your web forms and submit any data of their choosing.

Another reason you cannot rely on JavaScript to perform all your input validation is that some users disable JavaScript, or use browsers that don’t support it.

So the best types of validation to do in JavaScript are checking that fields have content if they are not to be left empty, ensuring that email addresses conform to the proper format, and ensuring that values entered are within expected bounds.

The validate.html Document (Part One)

Let’s begin with a general ...