Your crontab job is probably running just that you specified that you didn't want the output.
You are sending your output to /dev/null (> /dev/null) which is a way of stating you don't want the output saved unless there is a problem ( 2>&1). If you do want the output from the script, then don't point the output to /dev/null. Set up your entry to a log file of your own creation (such as /tmp/drpl_audit_log_script.log ). Read the man page on crontab