Redirect all the output as a block.
( yum -y update
service restart nginx
yum install atop
cat /var/log/somelog.log > /home/cron/php/script
) > /dev/null 2>&1
(
yum -y update
service restart nginx
yum install atop
cat /var/log/somelog.log > /home/cron/php/script
) > /dev/null 2>&1