I am working with Arduino library and PHP script whose allow secure? communication between Arduino and web server. Scripts works so that Arduino send data, which will be saved to text file in server and server respond with values from other text file in server. If you want to send new parameters to Arduino, just change values in the text file.
I am not professional programmer. You can find the first version, details and example code from http://code.google.com/p/arduino-web-data/
It is still under developing, but I need your feedback. All comments are welcome!