the answer is yes. by a number of different methods (as vacunita hints at)
1. you can create a serial interface to a phone that supports the AT character set for sending sms and use php to send information down the serial link (or control a com object that does this)
2. or, much easier, you can use an internet gateway service such as aql.com. for this service you can use php to post information to the aql gateway. it may also support a get method too. their api is published, of course.