<?php
$data = <<<DATA
<div>
<div data-cid="8558641" class="clsfd_list_row_group">
<div data-cid="12345" class="clsfd_list_row_group">
<div data-cid="123" class="clsfd_list_row_group">
</div>
DATA;
$dom = new DOMDocument();
$dom->loadHTML($data);
$xpath = new DOMXPath($dom);
$cids = $xpath->query("//div[@class='clsfd_list_row_group']/@data-cid");
foreach ($cids as $cid) {
echo $cid->nodeValue . "\n";
}
?>
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