title: What is required library needed for installing xmlreader in php:7.2-fpm-alpine custom docker image?
body: <p>For this composer <a href="https://github.com/PHPOffice/PhpSpreadsheet" rel="nofollow noreferrer">package</a> I need the xmlreader into my custom docker php image:</p>
  
  <pre><code>FROM php:7.2-fpm-alpine
  
  RUN apk add --update libzip-dev libmcrypt-dev libpng-dev libjpeg-turbo-dev libxml2-dev icu-dev postgresql-dev curl-dev libmemcached-dev &amp;&amp;\
      apk add --update --virtual build-dependencies build-base gcc wget autoconf &amp;&amp;\   
      docker-php-ext-install gd &amp;&amp; \
      docker-php-ext-install zip &amp;&amp;\
      docker-php-ext-install dom xml xmlwriter xmlreader &amp;&amp;\
      apk del build-dependencies &amp;&amp;\
      rm -rf /var/cache/apk/*
  </code></pre>
  
  <p>But when I build it I get the following error:</p>
  
  <pre><code>/usr/src/php/ext/xmlreader/php_xmlreader.c:32:10: fatal error: ext/dom/dom_ce.h: No such file or directory
   #include "ext/dom/dom_ce.h"
            ^~~~~~~~~~~~~~~~~~
  compilation terminated.
  make: *** [Makefile:194: php_xmlreader.lo] Error 1
  Removing intermediate container 0b3f031b2479
  
  </code></pre>
  
  <p>So I assume that I am missing some library but which one I am missing? </p>
  
  <p>The obviously <code>dom</code> extention that is also required Is installed via <code>docker-php-ext-install</code> and I also the reqwuired <code>libxml2-dev</code> is installed as well.</p>