What do you need for this project:
Machine-2-Machine (M2M) communication between two or more Arduinos over the internet. Control each pin or read values from any pin on the Arduino board, from your HTTP server anywhere on the web. Your web application can manage multiple Arduinos in a single application. Also, make a web interface to manually control your Arduinos. Currently, the RaspberryPi is acting only as a client towards the Arduino and the HTTP server in order to enable the communication end-to-end. Example, control a stepper motor from a webinterface or information from another Arduino.
Requirements:
PHP API examples: