What should be ideal output of a PHP script which is called by Cron on hourly basis?

You can log its output to a file for later debug and monitor.

You can do that from crontab:

* * * php /path/to/task1.php        >> /path/to/task1.log

As the cron runs without any user interaction, it doesn't really matter what output script gives. But, if you want to monitory progress of your cron scripts, add the relevant data for each cron job to a log file so you can evaluate how successful your cronjob is.