Thank you for your help! Much appreciated!
While testing the PHP script I never got it to work from the URL line when I used POST in the data retrieval. With GET it was simple to extract the data items and write these to a file on the server.
Why should there be a difference between GET and POST depending on what the data are used for?
Currently I will dump the data items to a text file for later analysis, but in the end there might be a database table to receive them so it is easier to show excerpts of data for varying time intervals.