title: Why does a PHP script constantly take up more memory?
body: <p>See this example:</p>
  
  <pre><code>echo memory_get_usage() . "\n"; // 36640
  $a = str_repeat("Hello", 4242);
  echo memory_get_usage() . "\n"; // 57960
  unset($a);
  echo memory_get_usage() . "\n"; // 36744
  </code></pre>
  
  <p>Can anyone explain why after un-setting the variable the memory usage does not return to 36640</p>