title: Geohash: How to calculate the eight surrounding boxes
body: <p>I use the code from <a href="https://github.com/davetroy/geohash-js" rel="nofollow">https://github.com/davetroy/geohash-js</a>
  But I don't know how to calculate the surrounding geohashcode of a given geohashcode.
  I need to use the function witch calculate them both in php and javascript.
  Does anyone have such code or some method to solve this problem?</p>