master slave for gprs

I am doing some tests on the arduino, especially with the GPRS module. I have 2 modules Arduinos one with gprs modules, and hosting with php pages and mysql db.

My idea is that the Arduino is connected to the web, and send their data such as the current state of digital input, every so often, such as 1 minute.

an example similar to that found him at: (Uploading Sensor Data to using GPRS) to send temperature data to a website. or the following to send data to twitter

but I want to go further, can send commands from the Arduino website through this link was established, for example to change the status of a digital output. in sum, would be a back and forth communication.

I did a test and it worked was as follows: (the arduino receives commands via text message). much more expensive but do it by text message, and it becomes slow. I think it would be best done by gprs

Could you please help me with some comment about

Pablo Núñez Paraguay

I looking for the same answers. If you got idea how to make this - tell me.