We have recently upgraded to CiviCRM 4.7.0, and we have Drupal 7.41
As part of the upgrade process, I upgraded PHP to 5.6.17
Most things work brilliantly, but when we have link tracking enabled on a CiviMail email we get this error:
Fatal error: Call to undefined function drupal_add_http_header() in /home/ace/public_html/sites/all/modules/civicrm/CRM/Utils/System/Drupal.php on line 789
There's nothing recorded in the HTTP Error Log - can anyone give me any clues on debugging this error?