If you want to implement licensing module in downloadable php application that need:
I have taken advantage of the latest version of PHP 5.6 which has some new features that can be leveraged in to a licensing and distribution trialware. You can now distribute password protected files and demo applications.
Since there are some best practices to doing this correctly. I am distributing a demonstration website application showing how to setup your apps so they can be launched and checked in real-time for licenses codes just like a desktop application. As a matter of fact the protection extends to the desktop. I am selling the initial code to developers via binpress.com at fhqk.binpress.com. The online demo is http://fhqk.com/informationtechnology/ssl (Simple Secure Licensing)