title: Why redeclare a PHP variable if it is found to be null with the same null value?
body: <p>Whilst working within Magento I have begun seeing a pattern throughout the core coding. However, it is something I have seen throughout many areas of PHP coding. When a variable is declared in a function, it can then be used. An example of this is within magento, whilst emulating the store there is this code:</p>
  
  <pre><code>    public function startEnvironmentEmulation(
          $storeId, 
          $area = Mage_Core_Model_App_Area::AREA_FRONTEND,
          $emulateSroreInlineTranslation = false
      ) {
          if (is_null($area)) {
              $area = Mage_Core_Model_App_Area::AREA_FRONTEND;
          }
             ...
             ...
  </code></pre>
  
  <p><br>
  You can see that <code>$area</code> is defined, and then re-defined if it is found to be null.</p>
  
  <p>Is it important to re declare the same variable if it is found to be null, as a kind of re-try? Or am I missing something?</p>
  
  <p>Any help in understanding this would be appreciated!</p>