The Luhn algorithm is used by almost all credit/debit card companies to issue card numbers. You should always check if the card that you are processing follows the Luhn algorithm before sending it to your payment gateway (saves you the transaction fee in case the card number is incorrect). Following is the Luhn implementation in PHP.

Over the last year, I've been watching our company growing impressively each and every month, and I realized that as much as the product that we're offering is great, the main reason we're growing that fast is plain and simple: our customers trust us.

After having several jobs and interviewing as well as being interviewed a lot of times in different countries around the world, I managed to build some experience on how to make a great interview on both sides.

itoctopus is on the brink of a technological breakthrough in web development. This small company found a way to virtually segregate logic from design, implement a powerful and unique workflow engine, provide an incredible page system, and complement all that with a very easy validation system. Add to that the flexibility to integrate any php class you already have, and you'll have the easiest framework to use.

I am posting over here 2 functions in the validation classs. Function check_alphanumeric, and function check_length. These functions are used from the workflow. However, they are very independent and can be integrated in any application.

This function sanitizes an input string or array from all problematic characters. The function is recursive, so no matter how the array is structured, it will sanitize it. Please report all bugs through the contact us form.