title: Does really SplFixedArray perform better than arrays?
body: <p>I'm testing the SplFixedArray building an array with the days of the week, and I get the following results:</p>
  
  <pre><code>&lt;?php
  
  $days = new SplFixedArray(7);
  
  $days[0] = "Monday";
  $days[1] = "Tuesday";
  $days[2] = "Wednesday";
  $days[3] = "Thursday";
  $days[4] = "Friday";
  $days[5] = "Saturday";
  $days[6] = "Sunday";
  
  echo memory_get_peak_usage() . "\n"; //Returns 327688
  echo memory_get_usage() . "\n"; //Returns 327140
  echo memory_get_peak_usage(true) . "\n"; //Returns 524288
  echo memory_get_usage(true) . "\n"; //Returns 524288 
  </code></pre>
  
  <p>With traditional arrays:</p>
  
  <pre><code>&lt;?php
  
  $days = array();
  
  $days[0] = "Monday";
  $days[1] = "Tuesday";
  $days[2] = "Wednesday";
  $days[3] = "Thursday";
  $days[4] = "Friday";
  $days[5] = "Saturday";
  $days[6] = "Sunday";
  
  echo memory_get_peak_usage() . "\n"; //Returns 327528
  echo memory_get_usage() . "\n"; //Returns 326820
  echo memory_get_peak_usage(true) . "\n"; //Returns 524288
  echo memory_get_usage(true) . "\n"; //Returns 524288
  </code></pre>
  
  <p>Does it make sense for you?</p>