PHP Logo

Don't Validate And Format In A Single Function

30th June 2018 - 5 minutes read time

I wanted to impart a piece of advice to do with validation and formatting of user input, although I've never seen anyone suggest it. I guess it would come under the single responsibility principle so it might seem obvious to some people. There can be reasons why this might at least seem like a good idea at the time.

Essentially, if you want to validate that something is correct, don't format it at the same time. These two actions should be done in separate functions or even classes. I hope to demonstrate that using a single function validate and format anything is a bad idea. I'll mainly be using PHP to demonstrate this, but the principle should be pretty much the same in any language.

Take the following function called isValid(). This is an arbitrary and simple example but shows validation and formatting in use in a single function.

PHP Logo

UK PostCode Validation Function In PHP

21st May 2012 - 5 minutes read time

Creating a function to validate UK postcodes would seem like a simple task, but there is a little more to it than checking the number of characters. In fact there are several different variants of UK postal codes, especially if you include BFPO and overseas addresses. The official postcode specification details the structure of the postcode, and there is also a list of BFPO numbers from