I have an idea and I would like to be able to send USSD commands and receive USSD responses using a GSM SIM card via PHP.
Such as
Example Command
*555*
Example Response from GSM provider
1. Recharge Account
2. Send Credits
3. Service Menu
Example Reply Command
1
and the flow goes on.
Is this doable? What kind of hardware/modem do I need to get started? Can any one give me some tips?