Pull database configs into a Symfony app using symfony/flex on Platform.sh

doctrine.yaml

# file: config/packages/doctrine.yaml

parameters:
    # Adds a fallback DATABASE_URL if the env var is not set.
    # This allows you to run cache:warmup even if your
    # environment variables are not available yet.
    # You should not need to change this value.
     env(DATABASE_URL): ''

doctrine:
    dbal:
        url: '%env(DATABASE_URL)%'

parameters_platform.php

<?php

# file: config/parameters_platform.php

$relationships = getenv("PLATFORM_RELATIONSHIPS");
if (!$relationships) {
    return;
}

$relationships = json_decode(base64_decode($relationships), TRUE);

foreach ($relationships['database'] as $endpoint) {

    if (empty($endpoint['query']['is_master'])) {
        continue;
    }

    // setup database url for environment with platform.sh env var
    $database_url = "{$endpoint['scheme']}://{$endpoint['username']}:{$endpoint['password']}@{$endpoint['host']}:{$endpoint['port']}/{$endpoint['path']}";

    // pass the parameter to the app
    $container->setParameter('env(DATABASE_URL)', $database_url);
}

# Store session into /tmp.
ini_set('session.save_path', '/tmp/sessions');

services.yaml

# file: config/services.yaml

imports:
    - { resource: 'parameters_platform.php', ignore_errors: true }