alternative way for language filter redirects (as discussed in 11196)

plugins/system/languagefilter/languagefilter.php

@@ -401,13 +401,36 @@ public function parseRule(&$router, &$uri)
 					$uri->setPath('index.php/' . $uri->getPath());
 				}
 
-				$this->app->redirect($uri->base() . $uri->toString(array('path', 'query', 'fragment')), 301);
+				$redirectUri = $uri->base() . $uri->toString(array('path', 'query', 'fragment'));
 			}
 			else
 			{
 				$uri->setVar('lang', $this->lang_codes[$lang_code]->sef);
-				$this->app->redirect($uri->base() . 'index.php?' . $uri->getQuery(), 301);
+				$redirectUri = $uri->base() . 'index.php?' . $uri->getQuery();
 			}
+
+			// Set redirect HTTP code to "302 Found".
+			$redirectHttpCode = 302;
+
+			// If selected language is the default language redirect code is "301 Moved Permanently".
+			if ($lang_code === $this->default_lang)
+			{
+				$redirectHttpCode = 301;
+
+				// If configured to always use a sef prefix for default language we cannot cache this redirect in browser.
+				// 301 is cachable by default so we need to force to not cache it in browsers.
+				if ((int) $this->params->get('remove_default_prefix', 0) === 0)
+				{
+					$this->app->setHeader('Expires', 'Wed, 17 Aug 2005 00:00:00 GMT', true);
+					$this->app->setHeader('Last-Modified', gmdate('D, d M Y H:i:s') . ' GMT', true);
+					$this->app->setHeader('Cache-Control', 'no-store, no-cache, must-revalidate, post-check=0, pre-check=0', false);
+					$this->app->setHeader('Pragma', 'no-cache');
+					$this->app->sendHeaders();
+				}
+			}
+
+			// Redirect to language.
+			$this->app->redirect($redirectUri, $redirectHttpCode);
 		}
 
 		// We have found our language and now need to set the cookie and the language value in our system