title: What does |= means in PHP?
body: <p>PHP. Can somebody explain me what</p>
  
  <blockquote>
    <p>|=</p>
  </blockquote>
  
  <p>means in the following lines of code?</p>
  
  <pre><code>$mark = true;
  $options = FT_UID;
  if(!$mark) { 
    $options |= FT_PEEK;
  }
  </code></pre>
  
  <p>I've read |  is a <em>bitwise operation</em> which operates on bits but I still don't get it..</p>