title: how to check if object of a class already exists in PHP?
body: <p>consider the following code scenario:</p>
  
  <pre><code>&lt;?php
  
  //widgetfactory.class.php
  // define a class
  class WidgetFactory
  {
    var $oink = 'moo';
  }
  
  ?&gt;
  
  
  &lt;?php
  
  //this is index.php
  include_once('widgetfactory.class.php');
  
  // create a new object
  //before creating object make sure that it already doesn't exist
  
  if(!isset($WF))
  {
  $WF = new WidgetFactory();
  }
  
  ?&gt;
  </code></pre>
  
  <p>The widgetfactory class is in widgetfactoryclass.php file,  I have included this file in my index.php file, all my site actions runs through index.php, i.e. for each action this file gets included, now I want to create object of widgetfactory class ONLY if already it doesn't exist. I am using <code>isset()</code> for this purpose, is there any other better alternative for this?</p>