Before Fedora 27 only Symfony version 2.x (php-symfony) was available.  As of Fedora 27, 3 versions of Symfony will be available: 2.x (php-symfony), 3.x (php-symfony3*), and 4.x (php-symfony4*).  All versions can be installed at the same time.  If you have any issues with any of the Symfony versions/packages please create a bugzilla ticket.

Versions' root/base directories:

* 2.x: /usr/share/php/Symfony/

* 3.x: /usr/share/php/Symfony3/

* 4.x: /usr/share/php/Symfony4/