Send SMS from Mobile to Website and get response on Mobile about product

I have scenario, I want to facilitate to my customers to verify the product by sending product id from Mobiles SMS and my PHP website will verify that Id and will return the confirmation Message on Mobile by SMS.

Further understand the scenario in following 2 steps.

1. Send SMS Web(php)
2. Web will send back confirmation on SMS.

Please let me know, How can we accomplish this? How many entities will be involved in it.