PHP的SimpleXML:如何在名称中使用冒号

Question

我正在尝试使用SimpleXML生成RSS Google Merchant.

Google提供的示例是:

<?xml version="1.0"?>
<rss version="2.0" 
xmlns:g="http://base.google.com/ns/1.0">
<channel>
<title>The name of your data feed</title>
<link>http://www.example.com</link>
<description>A description of your content</description>
<item>
<title>Red wool sweater</title>
<link> http://www.example.com/item1-info-page.html</link>
<description>Comfortable and soft, this sweater will keep you warm on those cold winter nights.</description>
<g:image_link>http://www.example.com/image1.jpg</g:image_link> <g:price>25</g:price> <g:condition>new</g:condition> <g:id>1a</g:id>
</item>
</channel>
</rss>

我的代码有:

$product->addChild("g:condition", 'new');

哪个产生:

<condition>new</condition>

我在网上看到我应该使用:

$product->addChild("g:condition", 'new', 'http://base.google.com/ns/1.0');

现在生成:

<g:condition xmlns:g="http://base.google.com/ns/1.0">new</g:condition>

这对我来说似乎是非常反直觉的,因为现在"xmlns"声明几乎在我的RSS feed中的每一行都只有一次在根元素中.

我错过了什么吗？

Answer 1

正如@ceejayoz所说,您需要将"http://base.google.com/ns/1.0"命名空间添加到根节点,以便SimpleXML知道命名空间已经声明并且不会发出重复的前缀绑定.

我想您可能需要阅读有关XML命名空间的教程,因为我不确定您是否真的理解"g:"在这里做了什么.

这是一个更完整的例子.XML:

$xml = <<<EOT 
<?xml version="1.0"?> 
<rss version="2.0" xmlns:g="http://base.google.com/ns/1.0"> 
  <channel> 
    <title>The name of your data feed</title> 
    <link>http://www.example.com</link> 
    <description>A description of your content</description> 
    <item> 
      <title>Red wool sweater</title> 
      <link> http://www.example.com/item1-info-page.html</link> 
      <description>Comfortable and soft, this sweater will keep you warm on those cold winter nights.</description> 
      <g:image_link>http://www.example.com/image1.jpg</g:image_link> 
      <g:price>25</g:price> 
      <g:id>1a</g:id> 
    </item> 
  </channel> 
</rss> 
EOT 
; 

码:

$rss = new SimpleXMLElement($xml); 
$NS = array( 
    'g' => 'http://base.google.com/ns/1.0' 
); 
$rss->registerXPathNamespace('g', $NS['g']); 
$product = $rss->channel->item[0]; // example 

// Use the complete namespace. 
// Don't add "g" prefix to element name--what prefix will be used is 
// something SimpleXML takes care of. 
$product->addChild('condition', 'new', $NS['g']); 

echo $rss->asXML(); 

我通常使用这种模式来轻松处理命名空间:

$rss = new SimpleXMLElement($xml); 
$NS = array( 
    'g' => 'http://base.google.com/ns/1.0' 
    // whatever other namespaces you want 
); 
// now register them all in the root 
foreach ($NS as $prefix => $name) { 
    $rss->registerXPathNamespace($prefix, $name); 
} 
// Then turn $NS to an object for more convenient syntax 
$NS = (object) $NS; 
// If I need the namespace name later, I access like so: 
$element->addChild('localName', 'Value', $NS->g); 

Answer 2

这样做的诀窍:

$product->addChild('xmlns:g:condition', 'new'); 

Answer 3

您需要将该命名空间添加到父节点（最好是根节点）rss，以便子节点可以继承它，而不必每次都显式指定它。