use Zend\ServiceManager\ServiceLocatorInterface; class Example { protected $serviceManager; public function __construct(ServiceLocatorInterface $serviceManager) { $this->serviceManager = $serviceManager; } public function getService() { if ($this->serviceManager->has('service_name')) { return $this->serviceManager->get('service_name'); } else { return null; } } }In the example above, the has() method is used to check whether the service named "service_name" is registered in the service manager or not. If it is registered, the get() method is called to retrieve the instance of the service. Overall, the ServiceLocatorInterface interface in the Zend\ServiceManager package library of PHP is a powerful tool for retrieving instances of services and managing dependencies in an application.