title: How to implement "Maintenance Mode" on already established website
body: <p>I have built a website (PHP) with more than 60 pages. I have only now realized (unfortunately) that I should have built in an "In Maintenance Mode" feature to allow an admin to temporarily disable the website and point it to a Maintenance Mode page.  This would only allow those logged in as an admin to view the website.</p>
  
  <p>The options I see are:</p>
  
  <ol>
  <li><p>Add a new "include" file to the top of every single PHP page.</p></li>
  <li><p>I have one include that is used to display the navigation bar on<br>
  every page (navigation class).  I could write the Maintenance Mode<br>
  code in this class.</p></li>
  </ol>
  
  <p>Do I have any other options?  The 1st option doesn't seem like the most efficient, and the 2nd one just seems like bad programming.  Is there any other better way to include a new file on every single php file?</p>
  
  <p>Thanks!</p>
  
  <p>ps - the site is not launched yet</p>