title: What does 'field declared dynamically' mean in this situation?
body: <p>I'm pretty new to OOP and PHP. I'm using the IDE PhpStorm and it's giving me this (see below) warning on my reference to <code>$width</code>.</p>
  
  <p><img src="https://i.stack.imgur.com/iZm4M.png" alt="Warning &#39;Field declared dynamically&#39;"></p>
  
  <p>Here is my code:</p>
  
  <pre><code>&lt;?php
  class box {
      private $width;
  
      function __construct(){
          $this-&gt;width = 3;
      }
  }
  ?&gt;
  </code></pre>
  
  <p>I've never seen the term "field" used before, and I'm not entirely sure what the sentence "Field declared dynamically" means. </p>
  
  <p>It seems like this warning just showed up today after I updated PhpStorm. Did I do something wrong? </p>
  
  <p>Also, if anyone can briefly explain what the warning means by "Note: Check is not performed on objects of type "stdClass" or derived"?</p>