Use Docker env vars with PHP 5.2.x

most probably those env are overridden somewhere in image you are using.docker compose allows to define a command to run on startup. So you can override env vars on startup to whatever you need:

command: bash -c "DB_HOST='mariadb:3306' && DB_USER='some_user ... & ./start_something.sh"

EDIT:

as comment mentioned php require all env to be in php-fpm.conf. strange as for me but it's easy enough to work around by adding env vars you need into this file in same command: statement of docker compose. Simple echo "ENV_NAME" >> ..../php-fpm.conf should help you.

or you can modify Dockerfile so your image has simple sh script which would dump all env vars into that php config.

i am modifying mongo config so works as replica set - works like a charm.

I found an XML file at /usr/local/etc/php-fpm.conf that contained the Environment variables, and filled it in using dockerize

<value name="environment">    <!-- Add docker environment variables -->    {{ range $k,$v := .Env }}{{ $parts := split $k "APP_" }}{{ if eq (len $parts) 2 -}}    <value name="{{ index $parts 1 }}">{{ $v }}</value>    {{ end }}{{- end -}}    <!-- End Docker Env -->

With docker-compose having

environment:    APP_DB_HOST: mariadb:3306    APP_DB_USER: ${DB_USER}    APP_DB_PASSWORD: ${DB_PASSWORD}     APP_DB_DATABASE: ${DB_DATABASE}