command-prompt.sh

export BROWSER_REQUESTED='chrome' && phpunit

TestCase.php

class E2ETestCase extends PHPUnit_Framework_TestCase
{
    protected $driver; 
    
    public function setUp()
    {
        $this->driver = App_Factory_RemoteWebDriver::factory();
    }
    
    // more here.
}

WebDriverFactory.php

class App_Factory_RemoteWebDriver
{
    public static function factory()
    {
        switch ($_SERVER['BROWSER_REQUESTED']) {
            case 'chrome':
                return self::createChrome();
                break;
            case "ie":
                throw new Exception('Not implemented');
            break;
            
            case 'firefox':
            default:
                return self::createFirefox();
                break;
        }
    }

    public static function createChrome()
    {
        putenv("webdriver.chrome.driver=/path/to/chromedriver");

        $service = ChromeDriverService::createDefaultService();
        $service->start();
       
        return ChromeDriver::start(DesiredCapabilities::chrome(), $service);
    }

    public static function createFirefox()
    {
        // these are just constants defined in bootstrap.php 
        $seleniumUrl = isset($_SERVER['JENKINS_URL']) ? TEST_ENV_SELENIUM_SERVER : LOCAL_ENV_SELENIUM_SERVER;

        return RemoteWebDriver::create(
            $seleniumUrl, DesiredCapabilities::firefox()
        );
    }
}