如何合并具有相同属性的XML元素？

Question

I was wondering if is able to merge the following XML data on example.php file:

<?xml version="1.0" encoding="UTF-8"?>
<elevate>
 <query text="foo bar">
 <doc id="1"/>
 <doc id="2"/>
 <doc id="3"/>
</query>

<query text="foo bar">
 <doc id="4"/>
 <doc id="9"/>
 <doc id="3"/>
</query>
<elevate>

The result would be something like this:

<query text="foo bar">
 <doc id="1"/>
 <doc id="2"/>
 <doc id="3"/>
 <doc id="4"/>
 <doc id="9"/>
</query>

Answer 1

You could loop through the elements and create a "new" xml. Something like this?

$xml = <<<EOF
<?xml version="1.0" encoding="UTF-8"?>
<elevate>
    <query text="foo bar">
        <doc id="1"/>
        <doc id="2"/>
        <doc id="3"/>
    </query>

    <query text="foo bar">
         <doc id="4"/>
         <doc id="9"/>
         <doc id="3"/>
    </query>

    <query text="foo bar">
         <doc id="4"/>
         <doc id="8"/>
         <doc id="3"/>
    </query>
</elevate>
EOF;

$parsed = simplexml_load_string($xml);

$docs = [];

foreach ($parsed->query as $query) {
    foreach ($query->doc as $doc) {
        foreach ($doc->attributes() as $attribute) {
            // you should do some checking here, like in_array to make sure there is no duplicates.
            // we use __toString so it puts it as a string, not an XmlElement object
            $docs[] = $attribute[0]->__toString();
        }
    }
}

$docsXml = '';
foreach ($docs as $doc) {
    $docsXml .= '<doc id="' . $doc .'" />' . PHP_EOL;
}

$newXml = <<<EOF
<?xml version="1.0" encoding="UTF-8"?>
<elevate>
    <query text="foo bar">
     $docsXml
    </query>
</elevate>
EOF;

echo $newXml;

Which outputs

<?xml version="1.0" encoding="UTF-8"?>
<elevate>
    <query text="foo bar">
        <doc id="1" />
        <doc id="2" />
        <doc id="3" />
        <doc id="4" />
        <doc id="9" />
        <doc id="3" />
        <doc id="4" />
        <doc id="8" />
        <doc id="3" />

    </query>
</elevate>