Failed loading opcache.so on pmmp-phpstan:master

[SOF3]

# docker run --rm --volume $PWD:/source nxtlvlsoftware/pmmp-phpstan:master
PHP Warning:  Failed loading Zend extension 'opcache.so' (tried: /build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so (/build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so: cannot open shared object file: No such file or directory), /build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so.so (/build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0

Warning: Failed loading Zend extension 'opcache.so' (tried: /build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so (/build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so: cannot open shared object file: No such file or directory), /build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so.so (/build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
Running pmmp/phpstan analyzer
PHP Warning:  Failed loading Zend extension 'opcache.so' (tried: /build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so (/build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so: cannot open shared object file: No such file or directory), /build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so.so (/build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0

Warning: Failed loading Zend extension 'opcache.so' (tried: /build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so (/build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so: cannot open shared object file: No such file or directory), /build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so.so (/build/build/php/bin/php7/lib/php/extensions/no-debug-zts-20180731/opcache.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
File '/pocketmine/phpstan/rules/pm4-enum.phpstan.neon' is missing or is not readable.