I want to know the detail of the $eventdata variable in the function send_message($eventdata) in this file https://github.com/moodle/moodle/blob/master/message/output/email/message_output_email.php
I use "error_log('variable eventdata is: ' . print_object($eventdata));", but it only shows:
PHP message: variable eventdata is: stdClass Object
No internal detail info