One of our Amazon Linux servers has php56 installed, which is not the default PHP installation. Quite often I see updates for this package, while on other server PHP is not updated.
Do I need to restart the HTTPD service after updating php56?
You do not need to restart apache, but you need to tell it to reload its configuration. I am not sure which command centos uses to start/stop/reload daemons.
On centos the command should be:
sudo service httpd graceful
On a linux that uses systemd the command would be:
sudo systemctl reload apache2
On debian it would be:
sudo apache2ctl graceful