title: Need to send SMS alert 15 minutes before start of appointment
body: <p>I have an application in PHP that helps people fix appointments. </p>
  
  <p>How could I code to send SMS's 15 minutes before the start of the meeting time? </p>
  
  <p>I have code that takes care of sending SMS's. I just need to call the send method at the appropriate time.</p>