在 PHP 中使用 XPath 提取 XML [英] Using XPath to extract XML in PHP

问题描述

我有以下 XML:

<root>
   <level name="level1">
       <!-- More children <level> --> 
   </level>

   <level name="level2"> 
       <!-- Some more children <level> --> 
   </level> 
</root>

如何直接在 下提取 以便我可以运行 XPath 查询，例如 $xml->xpath('//some-query') 相对于提取的 ?

How can I extract a <level> directly under <root> so that I can run an XPath query such as $xml->xpath('//some-query') relative to the extracted <level>?

推荐答案

DOMXPath::query 的第二个参数是上下文节点.只需传递您之前找到"的 DOMNode 实例，您的查询就会相对"运行到该节点.例如

DOMXPath::query's second parameter is the context node. Just pass the DOMNode instance you have previously "found" and your query runs "relative" to that node. E.g.

<?php
$doc = new DOMDocument;
$doc->loadxml( data() );

$xpath = new DOMXPath($doc);
$nset = $xpath->query('/root/level[@name="level1"]');
if ( $nset->length < 1 ) {
    die('....no such element');
}
else {
    $elLevel = $nset->item(0);

    foreach( $xpath->query('c', $elLevel) as $elC) {
        echo $elC->nodeValue, "\r\n";
    }
}


function data() {
    return <<< eox
<root>
    <level name="level1">
        <c>C1</c>
        <a>A</a>
        <c>C2</c>
        <b>B</b>
        <c>C3</c>
    </level>
    <level name="level2"> 
        <!-- Some more children <level> --> 
    </level> 
</root>
eox;
}

<小时>

但是除非您必须执行多个单独的(可能是复杂的)后续查询，否则这很可能没有必要

---

But unless you have to perform multiple separate (possible complex) subsequent queries, this is most likely not necessary

<?php
$doc = new DOMDocument;
$doc->loadxml( data() );

$xpath = new DOMXPath($doc);
foreach( $xpath->query('/root/level[@name="level1"]/c') as $c ) {
    echo $c->nodeValue, "\r\n"; 
}


function data() {
    return <<< eox
<root>
    <level name="level1">
        <c>C1</c>
        <a>A</a>
        <c>C2</c>
        <b>B</b>
        <c>C3</c>
    </level>
    <level name="level2"> 
        <c>Ahh</c>
        <a>ouch</a>
        <c>no</c>
        <b>wrxl</b>
    </level> 
</root>
eox;
}

仅使用一个查询即可获得相同的输出.

has the same output using just one query.

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