Please try the DomDocument class:
<?php
$html = '<span class="vmshipment_name">Fragtmand</span>
<span class="vmshipment_description">Vi leverer i hele landet. Alle produkter fra Jabo, herunder hytter, havehegn osv. transporteres fra Sverige.<br>
Leveringstiden er ca. 12-18 dage.</span>';
$dom = new DomDocument();
$dom->loadHTML($html);
$xpath = new DOMXPath($dom);
$results = $xpath->query("//*[@class='vmshipment_name']");
echo $dom->saveHTML($results->item(0));
<span class="vmshipment_name">Fragtmand</span>