How to install PHP soap extension on Alpine 3.6

Question

I'm having issues trying to install and enable the PHP soap extension. I'm running the base image php:7.2-fpm-alpine3.6 inside a Docker container that has instructions like below in the Dockerfile. It's unclear to me how extensions are installed on Alpine. It seems to use docker-php-ext-install from what I can infer.

Dockerfile (I adopted this from somewhere):

RUN apk --no-cache add \
        freetype libpng libjpeg-turbo freetype-dev libpng-dev libjpeg-turbo-dev \
        wget \
        git \
        nginx \
        ca-certificates \
        supervisor \
        bash \
        nano \
    && docker-php-ext-install \
        mysqli \
        pdo_mysql \
        opcache \
        ...

So, I tried

docker-php-ext-install soap

which told me configure: error: xml2-config not found. Please check your libxml2 installation. I tried a bunch of stuff, but

apk add --no-cache libxml2-dev

seemed to do something. I followed this again with docker-php-ext-install soap, which outputted

Build complete.
Don't forget to run 'make test'.

Installing shared extensions:     /usr/local/lib/php/extensions/no-debug-non-zts-20170718/
find . -name \*.gcno -o -name \*.gcda | xargs rm -f
find . -name \*.lo -o -name \*.o | xargs rm -f
find . -name \*.la -o -name \*.a | xargs rm -f
find . -name \*.so | xargs rm -f
find . -name .libs -a -type d|xargs rm -rf
rm -f libphp.la       modules/* libs/*

At this point, I did not run make test, as it's unclear where I'm suppose to go find this Makefile. I searched under /usr/local/lib/php/extensions/no-debug-non-zts-20170718/, and soap.so was already there. Furthermore, my commands already enabled it for PHP-FPM. php -i showed /usr/local/etc/php/conf.d/docker-php-ext-soap.ini,.

I'm not entirely sure what I did. Is this (docker-php-ext-install) how you install extensions on this OS?

Answer 1

The PHP SOAP extension requires the PHP XML extension, as documented here: http://php.net/manual/en/soap.requirements.php

I expect you need to install that first.

Presumably docker-php-ext-install xml.

You shouldn't need to compile the XML library yourself as it will be part of the extension.