Check the nohup to see if works well.

check_nohup_sh.md

check_nohup.sh

#!/bin/bash
if
ps -ef | grep "send_confirm.php" | grep -v "grep"
then
echo “Running!”
else
echo “Stopped!”
cd /var/www/bdev/ubnt_email
nohup /usr/bin/php /var/www/bdev/ubnt_email/send_confirm.php >> /var/www/bdev/ubnt_email/mail.log &
fi

Then add this to the crontab

*/60 * * * * cd /var/www/bdev/ubnt_email && /bin/bash /var/www/bdev/ubnt_email/check_nohup.sh >> check.log

check the nohup shell for every 60 minutes. If stopped, it will do the nohup shell automatically.