title: What does false !== in a conditional statement with assignment cause?
body: <p>This seems to be a special case in some programming languages. In the php manual, I cannot find the meaning.</p>
  
  <pre><code>(false !== ($file = readdir($handle)))
  </code></pre>
  
  <p>There is an 'assignment on the right, comparison on the left, but what does the whole operator mean? </p>
  
  <p>Does using this have any special considerations?</p>