title: checking whether a form value has changed upon submit
body: <p>I'm creating a web app with Codeigniter, and I've created some edit forms (which pull current values from a mysql database). The user can edit the current database data by editing the data in the form. </p>
  
  <p>What I want to do is perform certain actions if the user changes certain values. So, I don't just want to perform the action when a field has a certain value, but only at the point when the user changes the value and submits the form. (Specifically, when the user indicates that she's performed a certain task by changing a value from "no" to "yes", then I want to do things like set a timestamp for the completion of the task, etc.)</p>
  
  <p>I've tried googling a solution, but I'm having trouble finding what I need. Can anyone point me in the right direction?</p>