Fix Engelsystem.de iCal Export for Google Calendar subscribe.

engelsystem.php

<?php
  $url = 'https://engelsystem.de/30c3/?p=ical&key=<yourapikey>'; //The URL
  $curl = curl_init();
  
  curl_setopt($curl, CURLOPT_URL, $url);
  curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, 0); //Accept the invalid certificate
  curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1); //push ical into variable

  $result = curl_exec($curl); //fetch it!
  
  curl_close($curl);
  header("Content-Type: text/Calendar"); //return the right mime-type
  header("Content-Disposition: inline; filename=engelsystem.ics"); 
  $trimmed = trim($result, "\x0A"); //remove "\n" at beginning of File


  echo($trimmed);


?>