I have Roundcube installed on a KVM virtual server which had previously been running Ubuntu 14.04, but since that
version was EOL in April, I upgraded to 16.04, and immediately discovered that Roundcube (1.1.3) no longer worked.
After the upgrade, I am able to login to the login page of Roundcube, but after that I get a blank white screen. A check
of /var/log/apache2 shows the following
[Mon Jul 29 15:19:21.556281 2019] [:error] [pid 8941] [client xx.xx.xx.xx:51260] PHP Warning: Declaration of rcmail::get_instance($env = '') should be compatible with rcube::get_instance($mode = 0, $env = '') in /opt/www/roundcubemail-1.1.3/program/include/rcmail.php on line 30
Not a php programmer, so I'm not sure of what this is telling me... Prior to the Linux upgrade, Roundcube worked fine..