Magento 2 // Get Config Value

GetMagento2ConfigValue.php

<?php

use Magento\Framework\App\DeploymentConfig;
use Psr\Log\LoggerInterface;

class Config
{
    const MAGENTO_CLOUD_VARIABLES_KEY = 'MAGENTO_CLOUD_VARIABLES';
    const DEPLOYMENT_CONFIG_VARIABLES_KEY = 'caudalie';

    /** @var DeploymentConfig */
    private $deploymentConfig;

    /**
     * @var LoggerInterface
     */
    private $logger;

    /**
     * Config constructor.
     *
     * @param DeploymentConfig $deploymentConfig
     * @param LoggerInterface $logger
     */
    public function __construct(DeploymentConfig $deploymentConfig, LoggerInterface $logger)
    {
        $this->deploymentConfig = $deploymentConfig;
        $this->logger = $logger;
    }

    /**
     * Get environment variable
     * Check Cloud environment first then local then config.php
     *
     * @param $key
     * @return bool|mixed
     */
    public function getEnvironmentVariable($key)
    {
        try {
            if (getenv($key)) {
                return getenv($key);
            }

            // DEPLOYMENT config ?
            $variables = $this->deploymentConfig->get(self::DEPLOYMENT_CONFIG_VARIABLES_KEY, false);
            if ($variables && is_array($variables) && array_key_exists($key, $variables)) {
                return $variables[$key];
            }

            $this->logger->error("Environment variable [ $key ] not found!");
        } catch (\Exception $e) {
            $this->logger->error("Error while getting the environment variable [$key]", array('error' => $e));
        }
        return false;
    }
}