It was necessary recently to include short PHP tags since the site code that I transferred to another server was written with their use.
By default, they are disabled.
For example, the usual tags look like this:
<?php code ?>
And short ones like this:
<? code ?>
To include short ones, you need to find the short_open_tag parameter in the php.ini configuration file and specify its value in On, for example:
php.ini is usually located in the /etc/php5/directory, if cpanel is used, in /usr/local/lib/php.ini.
You need to reboot the web server to apply the change, in Ubuntu apache2 is rebooted with the command:
sudo service apache2 restart