I got an error saying php command not found are not allowed or something similar.
Please give the exact error.
Does the user who created the cronjob has the correct rights to run
Give the whole path to php, and create the cronjob as root
/usr/bin/php /home/site/domains/stie.be/public_html/admin/cronjobs/cronjob_daily_ssh.php > /tmp/log.txt 2>&1