你试过吗？试试这个例子（示例：添加数据标签）。

Did you try it? Try this example (Sample: adding data tags).

include 'simple_html_dom.php';

$html_string = '
<style>.myelems{color:green}</style>
<div>
    <p class="myelems">text inside 1</p>
    <p class="myelems">text inside 2</p>
    <p class="myelems">text inside 3</p>
    <p>simple text 1</p>
    <p>simple text 2</p>
</div>
';

$html = str_get_html($html_string);
foreach($html->find('div p[class="myelems"]') as $key => $p_tags) {
    $p_tags->{'data-index'} = $key;
}

echo htmlentities($html);

输出：

<style>.myelems{color:green}</style> 
<div> 
    <p class="myelems" data-index="0">text inside 1</p> 
    <p class="myelems" data-index="1">text inside 2</p> 
    <p class="myelems" data-index="2">text inside 3</p> 
    <p>simple text 1</p> 
    <p>simple text 2</p> 
</div>