Used widely in various recent applications, QR Codes can be seen on cola cans, business cards, in sushi bars, and in museums. QR Code is a 2-dimensional barcode specification that was invented in Japan. [...] In this article I'll show you how you can easily generate QR Codes from within your PHP application and share some ideas on how and when to use them, We'll be using PHP QR Code, a library written in PHP for generating QR Codes and which doesn't require any dependencies beyond the standard GD2 graphics extension for creating images.

Using the library makes things pretty easy - all you need to do is call the correct method related to the image type (like "png()" or "jpg()") for your desired output with the string you want to encode. You can also define things like the level of error correction of the result - related to how much data the image can store - and size.

The main point about 2-step verification is that something else than your computer provides that token. If it's on your computer and that one gets stolen (or hacked into), it won't help much for the additional security. That's why you need a second device for those tokens. Some banks do that with SMS/Text Messages (Facebook, too), other give you special devices for that (eg. RSA keys) and the last group does it with your smartphone.

At the request of a client, they created a tool that did just this, but for PHP. As a result, they created the GoogleAuthenticator library that makes it easy to implement in your application. There's even an example of it in use. For more information about the Google Authenticator tool, see this page on Google Code.

I was more interested in Semacode, because it looks somehow cooler than QR in my opinion. Unfortunately I wasn't able to find any free (beer and speech) PHP library to create these codes.

He did, however, find a Javascript port (from a C library) to harvest the logic from and create his own PHP class to handle the semacode creation. He notes that it's probably still a bit buggy but is offering it for download to whoever might want to mess around with it.