Drupal 7: Show full stacktrace on error

The drupaleers did not manage it in 7 years to show sensible stack traces in Drupal 7: https://www.drupal.org/project/drupal/issues/1158322

If you need a stack trace because you only get a generic "An unexpected error occured", patch drupal:

includes/bootstrap.inc, function _drupal_exception_handler: Before the _drupal_log_error call, do:

echo '<table border="1">' . $exception->xdebug_message . '</table>';

Requires xdebug.