Gists for blogpost

application.ini

[production]
settings.context.formats = "xml,json"

[staging : production]

[testing : staging]
settings.context.formats = "xml,json,html"

[development : testing]

Service_Controller_Action_Helper_RestContextSwitch.php

<?php

class Service_Controller_Action_Helper_RestContextSwitch extends Zend_Controller_Action_Helper_ContextSwitch
{
    
    public function getActionContexts($action = null)
    {
        // All actions point back to the global action, or return the complete list of actions
        return parent::getActionContexts($action ? 'global' : null);
    }

    // Every action has context
    public function hasActionContext($action, $context)
    {
        return true;
    }

    // It's not possible to add specific action contexts
    public function addActionContext($action, $context)
    {
        // You cannot add context to actions
        throw new Zend_Controller_Action_Exception('You must call addGlobalContext() instead of addActionContext()');
    }

    // Add global context, this will trigger for ALL actions found
    public function addGlobalContext($contexts)
    {
        return parent::addActionContext('global', $contexts);
    }

    // This is almosts an exact 1:1 copy of the Zend_Controller_Action_Helper_ContextSwitch::initContext().
    // We just need to modify 2 or 3 lines inside.
    public function initContext($format = null)
    {
        $this->_currentContext = null;

        $controller = $this->getActionController();
        $request    = $this->getRequest();
        $action     = $request->getActionName();

        // Return if no context switching enabled, or no context switching
        // enabled for this action
        $contexts = $this->getActionContexts($action);
        if (empty($contexts)) {
            return;
        }

        // Return if no context parameter provided
        if (!$context = $request->getParam($this->getContextParam())) {
            if ($format === null) {
                return;
            }
            $context = $format;
            $format  = null;
        }

        // Check if context allowed by action controller
        if (!$this->hasActionContext($action, $context)) {
            return;
        }

        // Return if invalid context parameter provided and no format or invalid
        // format provided
        if (!$this->hasContext($context)) {
            $context = $this->getDefaultContext();
        }

        // Use provided format if passed
        if (!empty($format) && $this->hasContext($format)) {
            $context = $format;
        }

        $suffix = $this->getSuffix($context);

        $this->_getViewRenderer()->setViewSuffix($suffix);

        $headers = $this->getHeaders($context);
        if (!empty($headers)) {
            $response = $this->getResponse();
            foreach ($headers as $header => $content) {
                $response->setHeader($header, $content);
            }
        }

        if ($this->getAutoDisableLayout()) {
            /**
             * @see Zend_Layout
             */
            // require_once 'Zend/Layout.php';
            $layout = Zend_Layout::getMvcInstance();
            if (null !== $layout) {
                $layout->disableLayout();
            }
        }

        if (null !== ($callback = $this->getCallback($context, self::TRIGGER_INIT))) {
            if (is_string($callback) && method_exists($this, $callback)) {
                $this->$callback();
            }
            else if (is_string($callback) && function_exists($callback))
            {
                $callback();
            }
            else if (is_array($callback))
            {
                call_user_func($callback);
            }
            else
            {
                /**
                 * @see Zend_Controller_Action_Exception
                 */
                // require_once 'Zend/Controller/Action/Exception.php';
                throw new Zend_Controller_Action_Exception(
                    sprintf('Invalid context callback registered for context "%s"', $context));
            }
        }

        $this->_currentContext = $context;
    }

}

Service_Controller_Plugin_AcceptHandler.php

<?php

class Service_Controller_Plugin_AcceptHandler extends Zend_Controller_Plugin_Abstract
{
    public function routeShutdown (Zend_Controller_Request_Abstract $request)
    {
        // Skip header check when we don't have a HTTP request (for instance: cli-scripts)
        if (! $request instanceof Zend_Controller_Request_Http) {
            return;
        }

        $this->getResponse()->setHeader('Vary', 'Accept');

        // Get the Accept header
        $header = $request->getHeader('Accept'); 
        switch (true) {
            // Depending on the value, set the correct format
            case (strstr($header, HTTP_HEADER_APPLICATION_TYPE.'+json')) :
                $request->setParam('format', 'json');
                break;
            case (strstr($header, HTTP_HEADER_APPLICATION_TYPE.'+xml')) :
                $request->setParam('format', 'xml');
                break;
            case (strstr($header, HTTP_HEADER_APPLICATION_TYPE.'+html')) :
                $request->setParam('format', 'html');
                break;
            default:
                // Default: return whatever is default, but only when the format is not set
                $format = $request->getParam('format');
                if (! isset ($format)) {
                    /* Format is not found, so we use HTML. Used so we don't need to specify
                     * a format when checking the REST server at the browser */
                    $request->setParam('format', 'html');
                }
                break;
        }
    }
}

Service_Controller_Plugin_Mediaformat.php

<?php

class Service_Controller_Plugin_Mediaformat extends Zend_Controller_Plugin_Abstract
{

    public function routeShutdown(Zend_Controller_Request_Abstract $request)
    {
      $config = Zend_Config::getConfig();

      // Check if format is valid
      $format = $request->getParam('format');
      if (! in_array($format, explode(',', $config->settings->context->formats))) {
          // Trigger a HTTP 415 status code: MEDIA TYPE NOT SUPPORTED
      }
    }
}

Service_Rest_Controller.php

<?php

abstract class Service_Rest_Controller extends Zend_Controller_Action
{
    public function init()
    {
        // We remove ALL contexts before adding our own. This makes sure we ONLY use the contexts we supply here.
        $this->_helper->restContextSwitch()
            ->clearContexts()
            ->addContext(
                'xml',
                array('suffix' => 'xml', 'headers' => array('Content-Type' => 'text/xml')))
            ->addContext(
                'html',
                array('suffix' => '', 'headers' => array('Content-Type' => 'text/html')))
            ->addContext(
                'json',
                array('suffix' => 'json', 'headers' => array('Content-Type' => 'application/json')))
            ->clearActionContexts()
            ->addGlobalContext(array('xml', 'html', 'json'))
            ->setDefaultContext('xml')
            ->initContext();
    }

}