I have a Dockerfile with a build command like this:
Dockerfile
#install some base extensions RUN apt-get install -y \\ zlib1g-dev \\ zip \\
In case you are using 7.4 this worked for me:
FROM php:7.4-fpm-alpine RUN apk add --no-cache zip libzip-dev RUN docker-php-ext-configure zip RUN docker-php-ext-install zip RUN docker-php-ext-install pdo pdo_mysql