correct syntax for docker file alpine with --platform and php fpm-alpine

Question

What is the correct syntax to add a PHP version in docker file?

i have this syntax:

FROM --platform=linux/x86-64 alpine:3.11 php:7.4-fpm-alpine

WORKDIR /app

ENV LC_ALL en_US.UTF-8
ENV LANG en_US.UTF-8

RUN apk --no-cache add tzdata && \
    cp /usr/share/zoneinfo/Etc/UTC /etc/localtime && \
    echo "UTC" | tee /etc/timezone && \
    apk del tzdata

RUN apk --update add wget \
    curl \
    git \
    php7 \
    php7-opcache \
    php7-ctype \
    php7-xml \
    php7-xmlreader \
    php7-xmlwriter \
    php7-tokenizer \
    php7-pcntl \
    php7-json \
    php7-dom \
    php7-zip \
    php7-gd \
    php7-curl \
    php7-mbstring \
    php7-redis \
    php7-posix \
    php7-mcrypt \
    php7-iconv \
    php7-pdo_mysql \
    php7-phar \
    php7-simplexml \
    php7-openssl \
    php7-sockets \
    php7-fileinfo && rm /var/cache/apk/*

The problem with this syntax is I am getting an error on this line: FROM --platform=linux/x86-64 alpine:3.11 php:7.4-fpm-alpine

What is the correct syntax to add a PHP version in my docker file?

Thanks!

Answer 1

FROM only accepts one or three arguments and --platform=linux/x86_64 is a modifier not an argument so split it onto two lines.

FROM --platform=linux/x86_64 alpine:3.11
FROM php:7.4-fpm-alpine

Although, according to the Official Docs, you probably only want FROM php:7.4-fpm-alpine unless you have another reason for wanting things that are available on the alpine:3.11 image that are not on the php:7.4-fpm-alpine image.

Adding my changes to the your Dockerfile results in the below. I have tested this and docker build ./ works with this file in an empty directory.

 FROM --platform=linux/x86-64 alpine:3.11 
 FROM php:7.4-fpm-alpine
 
 WORKDIR /app
 
 ENV LC_ALL en_US.UTF-8
 ENV LANG en_US.UTF-8
 
 RUN apk --no-cache add tzdata && \
     cp /usr/share/zoneinfo/Etc/UTC /etc/localtime && \
     echo "UTC" | tee /etc/timezone && \
     apk del tzdata
 
 RUN apk --update add wget \
     curl \
     git \
     php7 \
     php7-opcache \
     php7-ctype \
     php7-xml \
     php7-xmlreader \
     php7-xmlwriter \
     php7-tokenizer \
     php7-pcntl \
     php7-json \
     php7-dom \
     php7-zip \
     php7-gd \
     php7-curl \
     php7-mbstring \
     php7-redis \
     php7-posix \
     php7-mcrypt \
     php7-iconv \
     php7-pdo_mysql \
     php7-phar \
     php7-simplexml \
     php7-openssl \
     php7-sockets \
     php7-fileinfo && rm /var/cache/apk/*

As an additional recommendation, and this is more a "consistency" thing than a "your build will break soon" because PHP 7.4 is in LTS and there will be no PHP 7.5. You may want to change FROM php:7.4-fpm-alpine to FROM php:7-fpm-alpine as you're intstalling php7-* packages which will technically take the latest compatible version 7 package but your locking your php-fpm version to the latest 7.4 version.