How to install pgsql driver on docker php:7.1-apache?

That means that PSQL is working properly but in order to apache to work properly you will need to add the psql libraries and drivers :

FROM php:7.1-apache# PHP extensionsENV APCU_VERSION 5.1.7RUN buildDeps=" \        libicu-dev \        zlib1g-dev \        libsqlite3-dev \        libpq-dev \    " \    && apt-get update \    && apt-get install -y --no-install-recommends \        $buildDeps \        libicu52 \        zlib1g \        sqlite3 \        git \        php5-pgsql \    && rm -rf /var/lib/apt/lists/* \    && docker-php-ext-install \        intl \        mbstring \        pdo_mysql \        pdo_pgsql \        pdo \        pgsql \        zip \        pdo_sqlite \    && apt-get purge -y --auto-remove $buildDepsRUN pecl install \        apcu-$APCU_VERSION \        xdebug \    && docker-php-ext-enable xdebug \    && docker-php-ext-enable --ini-name 05-opcache.ini \        opcache \    && docker-php-ext-enable --ini-name 20-apcu.ini \        apcuARG SYMFONY_ENV=devENV SYMFONY_ENV=devRUN if [ "$SYMFONY_ENV" -ne "dev" ]; then \        sed -i '1 a xdebug.remote_enable=1' /usr/local/etc/php/conf.d/docker-php-ext-xdebug.ini && \        sed -i '1 a xdebug.remote_handler=dbgp' /usr/local/etc/php/conf.d/docker-php-ext-xdebug.ini && \        sed -i '1 a xdebug.remote_autostart=0' /usr/local/etc/php/conf.d/docker-php-ext-xdebug.ini && \        sed -i '1 a xdebug.remote_connect_back=1 ' /usr/local/etc/php/conf.d/docker-php-ext-xdebug.ini && \        sed -i '1 a xdebug.remote_port=9001' /usr/local/etc/php/conf.d/docker-php-ext-xdebug.ini && \        sed -i '1 a xdebug.remote_log=/var/log/xdebug_remote.log' /usr/local/etc/php/conf.d/docker-php-ext-xdebug.ini; \    fi;# Apache configRUN a2enmod rewriteADD docker/apache/vhost.conf /etc/apache2/sites-available/000-default.conf# PHP configADD docker/php/php.ini /usr/local/etc/php/php.ini# Add the applicationADD . /appWORKDIR /appRUN chmod +x /app/docker/composer.sh# Install composerRUN /app/docker/composer.sh \    && mv composer.phar /usr/bin/composer \    && composer global require "hirak/prestissimo:^0.3"ENV PATH="$PATH:$HOME/.composer/vendor/bin"# to defineARG INSTALL_DEP=trueRUN if [ -n "$INSTALL_DEP" ]; then \    if [ "$SYMFONY_ENV" -ne "prod" ]; then \        composer install --prefer-dist --no-scripts --no-dev --no-progress --no-suggest --optimize-autoloader --classmap-authoritative && composer run-script continuous-pipe; \    else \    composer install -o --no-interaction --prefer-dist --no-scripts && composer run-script continuous-pipe; \    fi; \    fi;# Remove cache and logs if some and fixes permissionsRUN rm -rf var/cache/* && rm -rf var/logs/* && rm -rf var/sessions/* && chmod a+r var/ -R# Apache gets grumpy about PID files pre-existingRUN rm -f /var/run/apache2/apache2.pidRUN a2enmod sslEXPOSE 443CMD ["/app/docker/apache/run.sh"]

This should be working properly and you could compare with ur existing configuration.