Environment variables

All preview containers receive a set of PREV_* environment variables. They are available in PHP via getenv() and in deploy scripts as shell variables.

---

General

Variable	Description	Example
PREV_IS_PREVIEW	Flag indicating the app is running inside a preview environment.	"true"
PREV_PROJECT_NAME	Project slug as configured in Preview Manager.	"my-drupal-site"
PREV_PREVIEW_NAME	Preview identifier. MR previews use mr-{iid}, branch previews use branch-{name}.	"mr-42" or "branch-develop"
PREV_MR_IID	GitLab merge request IID. Empty for branch previews.	"42"
PREV_BRANCH	Git branch name that this preview was built from.	"feature/new-module"
PREV_COMMIT_SHA	Full git commit SHA of the deployed code.	"a1b2c3d4e5f6..."

---

URLs & domains

Variable	Description	Example
PREV_URL	Full preview URL including protocol. Use for absolute links and drush URI.	"https://mr-42-my-site.druploy.dev"
PREV_DOMAIN	Preview domain without protocol. Used in trusted_host_patterns.	"mr-42-my-site.druploy.dev"
PREV_DOMAIN_ALIASES	Comma-separated list of alias domains. Set when domain_aliases configured in druploy.yml. Each alias becomes {alias}--{domain}.	"admin--mr-42-my-site.druploy.dev,fr--mr-42-my-site.druploy.dev"

---

Database

Variable	Description	Example
PREV_DB_HOST	Database container hostname. Points to the MySQL/MariaDB container.	"mr-42-my-site-db"
PREV_DB_NAME	Database name.	"drupal"
PREV_DB_USER	Database username.	"drupal"
PREV_DB_PASSWORD	Database password.	"drupal"

Note

All previews use the same credentials (drupal/drupal). The database runs in an isolated container per preview, so there is no conflict.

---

File paths

Variable	Description	Example
PREV_FILE_PUBLIC_PATH	Drupal public files directory, relative to docroot.	"sites/default/files"
PREV_FILE_PRIVATE_PATH	Drupal private files directory, relative to docroot.	"sites/default/files/private"
PREV_FILE_TEMP_PATH	Temporary files directory (absolute path).	"/tmp"
PREV_FILE_TRANSLATIONS_PATH	Interface translation files directory, relative to docroot.	"sites/default/files/translations"

---

Optional services

These variables are only set when the corresponding service is enabled in druploy.yml.

Variable	Description	Example
PREV_REDIS_HOST	Redis/Valkey container hostname. The settings.druploy.php auto-configures the Redis cache backend when set.	"mr-42-my-site-redis"
PREV_SOLR_HOST	Apache Solr container hostname.	"mr-42-my-site-solr"
PREV_SOLR_CORE	Solr core name.	"drupal"
PREV_LITESPEED_CACHE	Flag indicating LiteSpeed Cache is enabled in the web server.	"1"

---

Proxy

Variable	Description	Example
PREV_HTTP_PROXY	HTTP proxy URL. Set when the preview VM uses a proxy for outbound traffic.	"http://proxy:3128"
PREV_HTTPS_PROXY	HTTPS proxy URL. Same value as PREV_HTTP_PROXY.	"http://proxy:3128"

These are also passed to git clone and other build-time operations.

---

Custom variables

You can define custom environment variables in druploy.yml under the env: key. These are injected as-is into the PHP container, without the PREV_ prefix.

# druploy.yml
env:
  APP_ENV: preview
  STAGE_FILE_PROXY_ORIGIN: "https://example.com"
  MY_API_KEY: "abc123"

Access them in PHP or scripts the same way:

$env = getenv('APP_ENV');                        // "preview"
$origin = getenv('STAGE_FILE_PROXY_ORIGIN');

---

Usage examples

In settings.druploy.php (PHP)

// Database connection.
$databases['default']['default'] = [
  'database' => getenv('PREV_DB_NAME'),
  'username' => getenv('PREV_DB_USER'),
  'password' => getenv('PREV_DB_PASSWORD'),
  'host'     => getenv('PREV_DB_HOST'),
  'port'     => '3306',
  'driver'   => 'mysql',
];

// Trusted host.
$settings['trusted_host_patterns'][] =
  '^' . preg_quote(getenv('PREV_DOMAIN')) . '$';

// Conditional: detect preview environment.
if (getenv('PREV_IS_PREVIEW')) {
  $config['system.performance']['css']['preprocess'] = FALSE;
  $config['system.performance']['js']['preprocess'] = FALSE;
}

In deploy scripts (Bash)

#!/usr/bin/env bash
set -euo pipefail

echo "Deploying $PREV_PROJECT_NAME preview $PREV_PREVIEW_NAME"
echo "Branch: $PREV_BRANCH (commit: $PREV_COMMIT_SHA)"
echo "URL: $PREV_URL"

vendor/bin/drush deploy

# Warm the cache.
curl -s "$PREV_URL" > /dev/null

Checking for optional services

// Redis — only configure if the service is running.
if (getenv('PREV_REDIS_HOST')) {
  $settings['redis.connection']['host'] = getenv('PREV_REDIS_HOST');
  // ... redis config
}

// Solr.
if (getenv('PREV_SOLR_HOST')) {
  $config['search_api.server.solr']['backend_config']['connector_config']['host']
    = getenv('PREV_SOLR_HOST');
}