Yes. There are a variety of companies that offer ways to send text messages from php pages. You would have to sign up for one of them and then generate a secret key on registration that you then send as text and then create a page where they can enter the text message value and compare it to the one you sent. Then mark a field in the database when they are "verified" and prevent login when that field isn't set.
Some easy and inexpensive implementations are:
It costs just a fraction of a penny to send each text, so the cost is really not a factor. This is something we could help you with in a premier support ticket if the implementation and associated php coding is over your head.