As much as programmers attempt to anticipate every possible action or combination of actions that a user can take when encountering a web application, no one can foresee them all. When the user takes an unanticipated course of action and "breaks" the application, the software needs to catch them before they fall.

They show you a few methods for handling the errors that might come up including the die function, exception handling, triggering errors and just outputting errors via an "echo" or "print" (or something similar).

One important use of Regular Expressions (Regex) is to verify fields submitted via a form. In this article, we attempt to write an expression that is able to verify the user's first name, middle name, last name or just names in general.

The expression should allow names such as "Mary", "Mr. James Smith" and "Mrs O'Shea" for example. So the challenge here is to allow spaces, periods and single quotation marks in the name field and reject any other characters.

Their examples use the preg_* functions in PHP to work, first looking for any invalid characters in the string(s), then amending it to ensure that there aren't any numbers involved either. The few lines of code it takes are included as well.