删除除PHP中第一个以外的所有列表元素？

Question

How do I remove all the li elements except the first in PHP?

<div class="category">
   <ul class="products">
     <li>{nested child elements}</li>
     <li>{nested child elements}</li>
     <li>{nested child elements}</li>
   </ul>
</div>

The code above is generated by another script via a function.

The result should be like this:

<div class="category">
    <ul class="products">
        <li>{nested child elements}</li>
    </ul>
</div>

UPDATE: Sorry guys the "category" is a class not an ID.

In repay to Yoshi, ul.products has siblings but I didn't include them in my post. Would that affect the query?

This is how my code looks like with Yoshi's code added:

class Myclass {
    function prin_html() {
        $content = get_code();
        $dom = new DOMDocument;
        $dom->loadXml($content);

        $xpath = new DOMXPath($dom);
        foreach ($xpath->query('//li[position()>1]') as $liNode) {
            $liNode->parentNode->removeChild($liNode); 
        }

        echo $dom->saveXml($dom->documentElement);    
    }
}

It sill prints the non-filtered html code...

Answer 1

Try:

$dom = new DOMDocument;
$dom->loadHtml('<div id="category">
   <ul class="products">
     <li>{nested child elements}</li>
     <li>{nested child elements}</li>
     <li>{nested child elements}</li>
   </ul>
</div>');

$xpath = new DOMXPath($dom);
foreach ($xpath->query('//li[position()>1]') as $liNode) {
    $liNode->parentNode->removeChild($liNode);
}

$output = '';
foreach ($xpath->query('//body/*') as $child) {
    $output .= $dom->saveXml($child);
}

Output:

<div id="category">
   <ul class="products">
     <li>{nested child elements}</li>


   </ul>
</div>