title: PHP release memory of include file
body: <p>Can I release the memory generated from the included file, here are my codes</p>
  
  <p>a.php</p>
  
  <pre><code>&lt;?
  echo memory_get_usage();
  include_once "b.php";
  echo memory_get_usage();
  $n = new obj();
  echo memory_get_usage();
  ?&gt;
  </code></pre>
  
  <p>b.php</p>
  
  <pre><code>&lt;?
  class obj {
  protected $_obj = array{
  ....
  }
  
  function ....
  
  }
  
  ?&gt;
  </code></pre>
  
  <p>I checked that, after I include the b.php, the memory use will increase, which is more higher than create a new object. The result is as below</p>
  
  <p>348832
  496824
  497072</p>
  
  <p>So, how can I release the included file's memory?</p>