$re = '/(?<=pairValue">)(.*?)(?=<)/';
$str = '<h2>Køretøj</h2>
<div class="pairName">Mærke</div>
<div class="pairValue">PEUGEOT</div>
<div class="pairName">Model</div>
<div class="pairValue">607</div>
<div class="pairName">Stelnummer</div>
<div class="pairValue">VFDDD4TZE92104255</div>
<div class="pairName">Seneste reg.nr.</div>
<div class="pairValue">YE45522</div>';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php