Store and return zend template as a variable instead of printing it to the browser

Below is the code for your controller in which I am return the phtml in JSON. It can we used for AJAX:

use Zend\View\Model\ViewModel;
use Zend\View\Model\JsonModel;
use Zend\View\Renderer\PhpRenderer;
use Zend\View\Resolver;

public function searchClientAction()
{ 
     $renderer = new PhpRenderer();
     $map = new Resolver\TemplateMapResolver(array(
         'client_search' => __DIR__ . '/../../../view/Client/Client/prepareHTML.phtml',

     ));

     $resolver = new Resolver\TemplateMapResolver($map);
     $renderer->setResolver($resolver);

     $view = new ViewModel(array(
         'message' => 'Hello world',
     ));

     $view->setTemplate('client_search');

     $result = new JsonModel(array(
         'client_name' => $renderer->render($view),
         'success' => true,
     ));

     return $result;
}

Update module.config.php:

'view_manager' => array(
    .
    .
    .
    'strategies' => array(
            'ViewJsonStrategy',
    ),