Auto Direct message in response to Facebook page Like - repost

I am struggling with managing social marketing for one of my clients. I would like to start building an application to help automate some of the social media tasks. The first function I need is the ability to automatically respond with a direct message to a facebook page like. Therefore, I will need a single HTML page with PHP backend that allows: 1. The ability to register the software with an account 2. The ability to turn the auto-responder on/off 3. The ability to set the auto-responders direct message text This is clearly possible because there are services out there, but they have monthly costs involved. In the future I want more of these little scripts for Twitter, YouTube and other functions