You may solve it with adding a handler for php in the egroupware directory directive in /etc/httpd/conf.d/egroupware.conf
:
With php scl this should work for PHP 5.6:
<Directory /usr/share/egroupware>
...
<FilesMatch \.php$>
SetHandler "proxy:fcgi://127.0.0.1:9056"
</FilesMatch>
...
</Directory>
Apply config:
systemctl restart httpd