PHP 7 fpm, alpine, mongodb and composer

Dockerfile

FROM php:7-fpm-alpine

RUN apk --update add --virtual build-dependencies build-base openssl-dev autoconf \
  && pecl install mongodb \
  && docker-php-ext-enable mongodb \
  && apk del build-dependencies build-base openssl-dev autoconf \
  && rm -rf /var/cache/apk/*

# Time Zone
RUN echo "date.timezone=${PHP_TIMEZONE:-UTC}" > $PHP_INI_DIR/conf.d/date_timezone.ini

# Register the COMPOSER_HOME environment variable
ENV COMPOSER_HOME /composer

# Add global binary directory to PATH and make sure to re-export it
ENV PATH /composer/vendor/bin:$PATH

# Allow Composer to be run as root
ENV COMPOSER_ALLOW_SUPERUSER 1

# Setup the Composer installer
RUN curl -o /tmp/composer-setup.php https://getcomposer.org/installer \
  && curl -o /tmp/composer-setup.sig https://composer.github.io/installer.sig \
  && php -r "if (hash('SHA384', file_get_contents('/tmp/composer-setup.php')) !== trim(file_get_contents('/tmp/composer-setup.sig'))) { unlink('/tmp/composer-setup.php'); echo 'Invalid installer' . PHP_EOL; exit(1); }" \
  && php /tmp/composer-setup.php --install-dir=/usr/bin --filename=composer
  
# use composer this way: RUN composer require "mongodb/mongodb=^1.0.0"

or try this

RUN apk update \
    && apk add --no-cache \
    ${PHPIZE_DEPS} \
    && pecl install mongodb \
    && docker-php-ext-enable \
    mongodb \
    && apk del \
    ${PHPIZE_DEPS}

Many thanks !