title: Calling subclass's function from superclass based on string in PHP
body: <p>How would I do something like this:</p>
  
  <pre><code>&lt;?php
      class Controller
      {
          var $ActionName;
          var $PageParameters;
  
          function InvokeAction()
          {
              $actionFunctionName = ucfirst($this-&gt;ActionName);
  
              // Call a function named $actionFunctionName
                  // where $actionFunctionName is in a subclass
          }
  
      }
  ?&gt;
  </code></pre>
  
  <p>As a bonus, I would like to trap whether that function exists first.</p>