title: PHP profiling with microtime(): Negative time?
body: <p>For a very simple profiling I use <code>microtime()</code> like this:</p>
  
  <pre><code>$now = microtime();
  for (...) {
      // do something
      echo microtime() - $now;
      $now = microtime();
  }
  </code></pre>
  
  <p>Now, the output of the <code>echo</code> line seems completely random, that is, I expected fluctuations, but I <em>didn't</em> expect <em>negative numbers</em> showing up.</p>
  
  <p>However, a typical result contains ~ 1/3 negative numbers. I confirmed this on Solaris (PHP 5.0.x) and WinVista (PHP 5.2.3).</p>
  
  <p>What the heck is going on here? Have I invented accidently a time machine?</p>