Bug#816466: I had to additionally install libapache2-mod-php7 to get it working.

[積丹尼 Dan Jacobson]

Package: phpmyadmin
Version: 4:4.5.5.1-1

Depends: ... libapache2-mod-php7.0 | php7.0-cgi | php7.0-fpm | php7.0
is not enough.

I had to additionally install libapache2-mod-php7 to get it working.