First working release
The first release of the Weather Underground API client gives you some simple query methods to get weather data. The most simple setup looks like this:
// By default the current conditions will be requested in english language.
$weather = (new \lfischer\wunderground\API('<API-key here>'))->getByLocation('Germany', 'Dusseldorf');
There are a few default settings, you might want to check out (see the README)