Additional php versions and open_basedir
In default the open_basedir of a site points to the system-library of php.
When using a additional php version this one should be replaced with the library of this version. Eg,
/usr/share/php5:/usr/share/php: should be replaced with
/opt/php-7.1/lib/php (or whatever this version is installed).
This means: when activating a new php-version in config is a field missing for the
open_basedir restrictions of this version.
This moment a admin has to fix the oben_basedir entry of website when switching the php-version.