如何在php中获取xpath查询的结果？

问题描述：

I'm puzzled on how to extract the data from my xpath query. I'm using PHP 5.5.6 and I'm getting this result:

I'm all the countries:
DOMNodeList Object
(
    [length] => 0
)
1
I'm all the countries:
DOMNodeList Object
(
    [length] => 0
)
1
I'm all the countries:
DOMNodeList Object
(
    [length] => 0
)
1
I'm all the countries:
DOMNodeList Object
(
    [length] => 0
)
1

My XML file is (truncated to show only the first parts, I'm experimenting with large XML files):

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Data>
    <NewDataSet>
        <Table>
            <Country>Philippines</Country>
            <City>Subic Bay Weather Station</City>
        </Table>
        <Table>
            <Country>Philippines</Country>
            <City>Laoag</City>
        </Table>
        <Table>
            <Country>Philippines</Country>
            <City>Ninoy Aquino Inter-National Airport</City>
        </Table>
        <Table>
            <Country>Philippines</Country>
            <City>Davao Airport</City>
        </Table>
        <Table>
            <Country>Philippines</Country>
            <City>Clark Ab</City>
        </Table>
        <Table>
            <Country>Philippines</Country>
            <City>Legaspi</City>
        </Table>
        <Table>
            <Country>Philippines</Country>
            <City>Romblon</City>
        </Table>

And what I'm trying to do is to just show what's inside the Country tags via the xpath query. My code is:

<?php

    $reader = new XMLReader();
    $reader->open("countries.xml", "UTF-8");

    while($reader->read()){
        //echo var_dump($reader->nodeType), "<br/>";
        if($reader->nodeType == XMLReader::ELEMENT && $reader->localName == "Table"){
            $node = $reader->expand();
            $dom = new DOMDocument;
            $xp = new DomXPath($dom);
            $xp1 = $xp->query("//Country");
            echo "I'm all the countries: <pre>",print_r($xp1),"</pre>";

        }

    }

    $reader->close();


?>

I don't understand why I'm not getting a value for $xp1 that I can just use $xp1->nodeValue or $xp1->item(0)->nodeValue on. I've certainly tried, even though the returned object only had "length" to give back. I'm looking at the example Listing 5 on this site and it looks like I should be able to do this. What am I missing?

答

Your DOM is empty, you never add $node to it. Try:

$reader = new XMLReader();
$reader->open("countries.xml", "UTF-8");

while($reader->read()){
    if($reader->nodeType == XMLReader::ELEMENT && $reader->localName == "Table"){
        $node = $reader->expand();
        $dom = new DOMDocument;
        $n = $dom->importNode($node, true);
        $dom->appendChild($n);
        $xp = new DomXPath($dom);
        $xp1 = $xp->query("//Country");
        echo "I'm all the countries: <pre>{$xp1->item(0)->nodeValue}</pre>";

    }

}

$reader->close();

如何在php中获取xpath查询的结果？

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