Puoi usare una cosa tipo questa ( fa tutto SimpleXMLElement ):
Codice:
<?php
$xmlString = file_get_contents('https://api.weatherlink.com/v1/NoaaExt.xml?user=001D0A00DE6A&pass=DEMO&a%20piToken=demo0a002bc5272033001d0a002bc527');
$xmlData = new SimpleXMLElement($xmlString);
echo "credit=$xmlData->credit<br>";
echo "dewpoint=$xmlData->dewpoint_c<br>";
echo "dewpoint_day_high_f={$xmlData->davis_current_observation[0]->dewpoint_day_high_f}<br>";
?>