interface ProviderInterface
{

    const TYPE_ELECTRICITY = 'electricity';

    const TYPE_GAS = 'gas';

    /**
     * @param ContainerInterface $container
     *
     * @return void
     */
    function setContainer(ContainerInterface $container);

    /**
     * @return Client|SoapClient
     */
    function client();

}

trait ProviderTrait
{

    /**
     * @var string
     */
    private $endpoint = '';


    public function setContainer($container) {
        /** void for demo purposes */
    }
}


class Provider implements ProviderInterface
{

    use ProviderTrait;

    /**
     * @var string
     */
    private $username;

    /**
     * @var string
     */
    private $password;

    /**
     * constructor.
     *
     * @param ContainerInterface $container
     */
    final public function __construct(ContainerInterface $container)
    {
        $this->setContainer($container);

        /**
         * While $username and $password are declared within this class, the $endpoint is declared in the ProviderTrait. PHP works fine. PhpStorm ignores it and says it is declared "dynamically".
         */
        $this->endpoint = $this->container->getParameter('api.endpoint');
        $this->username = $this->container->getParameter('api.username');
        $this->password = $this->container->getParameter('api.password');
    }