Error.php

<?php
namespace MyApplication\Controller;
 
use Hydrogen\Controller;
use Hydrogen\MultiTemplateRenderer;
 
class Error extends Controller
{
    use MultiTemplateRenderer;
 
    public function error($message = "Server Error", $httpCode = 500)
    {
        // Checks for CLI automatically
        // Uses a config variable to map to template file types
        // (eg. CLI => ".cli.mustache")
        $this->render('error', compact($message, $httpCode));
    
    	return $this->response;
    }
}

MultiTemplateRenderer.php

<?php
namespace Hydrogen;

trait MultiTemplateRenderer
{
	protected function render($path, array $vars = [])
	{
        	// This part is still in the air
		$config = $this->__factory->Config->TemplateRenderer;
		$tr = $this->__factory->Hydrogen->TemplateRenderer;

		// Optionally modify the path based on config
		$realPath = $config->templatePath ?: __APP__.'/Template';
		$realPath .= $path;
		
		$map = [
			Request::INTERFACE_CLI => 'cli',
			Request::INTERFACE_HTTP => 'php_html'
		];
	        
	        $extension = $this->request->interface ?: Request::INTERFACE_HTTP;
	        $extension = $map[$extension];
	        $extension = $config->extensions->$extension;
	        
	        $realPath .= ".$extension";
	        
	        $this->response->setBody($tr->render($realPath, $vars));

		return $this->response;
	}
}