PHP SimpleXML错误消息

我通过

simplexml\u load\u file

加载一个ml文件，它有时有属性值，有时没有

用法：

Warning:  main() [function.main]: Node no longer exists

如何在没有得到警告的情况下检查是否存在值

---

谢谢

在使用该节点的任何方法之前，您必须检查该节点是否确实存在，例如：

$value = $xml->Name->arttributes();

Echo $value; 

是attributes（）方法没有返回值吗？看起来可能是未设置的$xml->Name。尝试检查是否设置了$xml->Name：

if (isset($xml->Name))
{
    $value = $xml->Name->attributes();
}

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一部纪录片。
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7.
5.
XML；
?>

到目前为止，我们只讨论了读取元素名称及其值的工作。SimpleXML还可以访问元素属性。访问元素的属性，就像访问数组的元素一样

我认为：

<?php
$xmlstr = <<<XML
<?xml version='1.0' standalone='yes'?>
<movies>
 <movie>
  <title>PHP: Behind the Parser</title>
  <characters>
   <character>
    <name>Ms. Coder</name>
    <actor>Onlivia Actora</actor>
   </character>
   <character>
    <name>Mr. Coder</name>
    <actor>El Act&#211;r</actor>
   </character>
  </characters>
  <plot>
   So, this language. It's like, a programming language. Or is it a
   scripting language? All is revealed in this thrilling horror spoof
   of a documentary.
  </plot>
  <great-lines>
   <line>PHP solves all my web problems</line>
  </great-lines>
  <rating type="thumbs">7</rating>
  <rating type="stars">5</rating>
 </movie>
</movies>
XML;
?>

<?php
include 'example.php';

$xml = new SimpleXMLElement($xmlstr);

/* Access the <rating> nodes of the first movie.
 * Output the rating scale, too. */
foreach ($xml->movie[0]->rating as $rating) {
    switch((string) $rating['type']) { // Get attributes as element indices
    case 'thumbs':
        echo $rating, ' thumbs up';
        break;
    case 'stars':
        echo $rating, ' stars';
        break;
    }
}
?> 

---

啊，你打败我了！我赞成这个答案

<?php
$xmlstr = <<<XML
<?xml version='1.0' standalone='yes'?>
<movies>
 <movie>
  <title>PHP: Behind the Parser</title>
  <characters>
   <character>
    <name>Ms. Coder</name>
    <actor>Onlivia Actora</actor>
   </character>
   <character>
    <name>Mr. Coder</name>
    <actor>El Act&#211;r</actor>
   </character>
  </characters>
  <plot>
   So, this language. It's like, a programming language. Or is it a
   scripting language? All is revealed in this thrilling horror spoof
   of a documentary.
  </plot>
  <great-lines>
   <line>PHP solves all my web problems</line>
  </great-lines>
  <rating type="thumbs">7</rating>
  <rating type="stars">5</rating>
 </movie>
</movies>
XML;
?>

<?php
include 'example.php';

$xml = new SimpleXMLElement($xmlstr);

/* Access the <rating> nodes of the first movie.
 * Output the rating scale, too. */
foreach ($xml->movie[0]->rating as $rating) {
    switch((string) $rating['type']) { // Get attributes as element indices
    case 'thumbs':
        echo $rating, ' thumbs up';
        break;
    case 'stars':
        echo $rating, ' stars';
        break;
    }
}
?> 

$attributeValue = isset($xml->attributes()->attributeName) ? $xml->attributes()->attributeName : null;