@martin In case it helps here is the dockerfile that I am using:
FROM library/php:7.1-apache
RUN apt-get update && apt-get -y install libldap2-dev libicu-dev libcurl4-openssl-dev libedit-dev libpng-dev libxml2-dev mysql-client libxrender1 libfontconfig1 libxext6 libfreetype6 fontconfig libjpeg62-turbo xfonts-75dpi xfonts-base
RUN docker-php-ext-configure ldap --with-libdir=lib/x86_64-linux-gnu/
RUN docker-php-ext-install mysqli pdo pdo_mysql ldap gd mbstring exif zip curl readline xml intl
RUN a2enmod headers rewrite
RUN cd /tmp && curl -GL -O https://github.com/wkhtmltopdf/wkhtmltopdf/releases/download/0.12.5/wkhtmltox_0.12.5-1.stretch_amd64.deb && dpkg -i wkhtmltox_0.12.5-1.stretch_amd64.deb && rm wkhtmltox_0.12.5-1.stretch_amd64.deb
VOLUME [“/var/www/html/”]