title: Measuring the time of PHP scripts - Using $_SERVER['REQUEST_TIME']
body: <p>Are this methods a reliable way to measure a script:</p>
  
  <p><code>$time = ($_SERVER['REQUEST_TIME_FLOAT'] - $_SERVER['REQUEST_TIME']);</code> </p>
  
  <p>or</p>
  
  <p><code>$time = (microtime(true) - $_SERVER['REQUEST_TIME_FLOAT']);</code> </p>
  
  <p>Which one should be used? </p>
  
  <p>And what's the difference of each one?</p>
  
  <p>They return very different measurements.</p>