Alpine v3.12:

FROM alpine:3.12

ADD https://dl.bintray.com/php-alpine/key/php-alpine.rsa.pub /etc/apk/keys/php-alpine.rsa.pub

RUN apk --update-cache add ca-certificates && \
    echo "https://dl.bintray.com/php-alpine/v3.12/php-7.4" >> /etc/apk/repositories

# install php and some extensions
RUN apk add --update-cache \
    php7 \
    php7-bz2 \
    php7-mysql \
    php7-any-other-available-package... 

Alpine v3.11:

FROM alpine:3.11

ADD https://dl.bintray.com/php-alpine/key/php-alpine.rsa.pub /etc/apk/keys/php-alpine.rsa.pub

RUN apk --update-cache add ca-certificates && \
    echo "https://dl.bintray.com/php-alpine/v3.11/php-7.4" >> /etc/apk/repositories

# install php and some extensions
RUN apk add --update-cache \
    php7 \
    php7-bz2 \
    php7-mysql \
    php7-any-other-available-package... 

Alpine v3.10:

FROM alpine:3.10

ADD https://dl.bintray.com/php-alpine/key/php-alpine.rsa.pub /etc/apk/keys/php-alpine.rsa.pub

RUN apk --update-cache add ca-certificates && \
    echo "https://dl.bintray.com/php-alpine/v3.10/php-7.4" >> /etc/apk/repositories

# install php and some extensions
RUN apk add --update-cache \
    php7 \
    php7-bz2 \
    php7-mysql \
    php7-any-other-available-package...