title: Underscore in php function
body: <p>What does it mean when a PHP function name begins with an underscore?</p>
  
  <p>for example: <code>__construct()</code></p>
  
  <p>I know what the construct means but I've seen other places where the function begins with an underscore, or a double underscore and I'm just not sure of the significance. </p>