simpleXML 和 XPaPath，读取同级

Question

我有以下XML文件：

<?xml version="1.0" encoding="UTF-8" ?>
<rss version="2.0">
<channel>
    <item>
        [...]
        <wp:postmeta>
            <wp:meta_key>_wp_old_slug</wp:meta_key>
            <wp:meta_value><![CDATA[item-1-slug]]></wp:meta_value>
        </wp:postmeta>
        <wp:postmeta>
            <wp:meta_key>_yoast_wpseo_title</wp:meta_key>
            <wp:meta_value><![CDATA[item-1-title]]></wp:meta_value>
        </wp:postmeta>
        [...]
    </item>
    <item>
        [...]
        <wp:postmeta>
            <wp:meta_key>_wp_old_slug</wp:meta_key>
            <wp:meta_value><![CDATA[item-2-slug]]></wp:meta_value>
        </wp:postmeta>
        <wp:postmeta>
            <wp:meta_key>_yoast_wpseo_title</wp:meta_key>
            <wp:meta_value><![CDATA[item-2-title]]></wp:meta_value>
        </wp:postmeta>
        [...]
    </item>
</channel>
</rss>

我正在循环浏览我的物品

$xmlurl = file_get_contents($xmlFile);
$xml = simplexml_load_string($xmlurl, null, LIBXML_NOCDATA);
$items = $xml->channel->item;
foreach( $items as $item ) {
}

在这个循环中，我想读取<wp:meta_key>_yoast_wpseo_title</wp:meta_key>节点的同级的值。例如，对于项目 1，我想获得"项目-1-标题"。我可能必须使用 xpath，但我真的不知道如何继续。

我该怎么做？

Answer 1

$xpath = './/wp:meta_key[text()="_yoast_wpseo_title"]/following-sibling::wp:meta_value[1]/text()';
$items = $xml->channel->item;
foreach( $items as $item ) {
  $result = $item->xpath($xpath);
  print "$result[0]n";
}
// => item-1-title
// => item-2-title

XPath 表达式的说明：

.                               - from the current node...
//wp:meta_key                   - get all descendant wp:meta_key nodes
[text()="_yoast_wpseo_title"]   - whose text content is _yoast_wpseo_title
/following-sibling::            - then get the siblings that come after this
wp:meta_value[1]                - with tag wp:meta_value; only take the first
/text()                         - and read its text

Answer 2

此解决方案包括对 Wordpress XML 命名空间的引用：

$doc = new SimpleXmlElement($xml);
$doc->registerXPathNamespace ('wp', 'http://wordpress.org/export/1.0/');
$wp_meta_title = $doc->xpath("//wp:postmeta[wp:meta_key = '_yoast_wpseo_title']/wp:meta_value");
foreach ($wp_meta_title as $title) {
    echo (string)$title . "n";
}

结果：

item-1-title
item-2-title

见 http://ideone.com/qjOfIW

//wp:postmeta[wp:meta_key = '_yoast_wpseo_title']/wp:meta_value路径非常简单，我认为不需要特别解释。