need twilio sms lead capture form

I need a web form that will ask a user for their cell number (u.s) and then when they click submit, will send their info (number) to my [login to view URL] account using the twilio api so that they will be subscribed to my sms list that I service with [login to view URL] For example, right now, I have to ask users to "Text 'coupon' to XXX-XXX-XXXX to sign up for text message coupons", and what I want to do is provide a simple form where they enter their cell number and press the submit button to subscribe instead. I would like this built with php/mysql.