- preg_match: documentation ( source)
<?php
$str = '<p class="geo"> <abbr class="latitude" title="52.19166">52.19166</abbr> <abbr class="longitude" title="-2.23108">-2.23108</abbr> </p>';
preg_match('/class="latitude"\s*title="([^"]+)"/', $str, $lat);
preg_match('/class="longitude"\s*title="([^"]+)"/', $str, $lon);
echo '<latitude>'.$lat[1].'</latitude>';
echo '<longitude>'.$lon[1].'</longitude>';