xml中的标记值保持不变（php + xml）

Question

我正在尝试更改标记值，但它不成功。这是我的xml格式和php代码，当我使用$ polls-＆gt; poll [0] - ＆gt; person [0] =＆＃34;更改＆＃34;时，它工作正常......：

＆＃13;

＆＃13;

$fname = getPollFile();
$polls = simplexml_load_file($fname);

foreach ($polls->poll as $poll){   
  foreach($poll->person as $person){
    $person = "process";
   }
}
   
$polls->asXML($fname);

＆＃13;

<?xml version="1.0" encoding="UTF-8"?>
<polls>
   <poll title="Ccccc">
      <person id="111">active</person>
      <person id="222">active</person>
   </poll>
</polls>

＆＃13;

＆＃13;

＆＃13;