title: Why php generator is slower than an array?
body: <p>According to comments from documentation: <a href="http://php.net/manual/en/language.generators.overview.php" rel="nofollow noreferrer">http://php.net/manual/en/language.generators.overview.php</a><br>
  We can see that thanks to generators there is huge memory usage improvement (which is obvious), but there is also 2-3 times slower execution - and that is not so obvious to me.</p>
  
  <p>We gain memory usage improvement at the expense of time - which is not fine.<br>
  So, why is php generator slower than an array?</p>
  
  <p>Thanks for tips.</p>