code: public function getFrontendUrl($strParams=null, $strForceLang=null)
  	{
  		if ($strForceLang !== null)
  		{
  			@trigger_error('Using PageModel::getFrontendUrl() with $strForceLang has been deprecated and will no longer work in Contao 5.0.', E_USER_DEPRECATED);
  		}
  
  		$this->loadDetails();
  
  		$objUrlGenerator = System::getContainer()->get('contao.routing.url_generator');
  
  		$strUrl = $objUrlGenerator->generate
  		(
  			($this->alias ?: $this->id) . $strParams,
  			array
  			(
  				'_locale' => ($strForceLang ?: $this->rootLanguage),
  				'_domain' => $this->domain,
  				'_ssl' => (bool) $this->rootUseSSL,
  			)
  		);
  
  		// Make the URL relative to the base path
  		if (0 === strncmp($strUrl, '/', 1))
  		{
  			$strUrl = substr($strUrl, \strlen(Environment::get('path')) + 1);
  		}
  
  		$strUrl = $this->applyLegacyLogic($strUrl, $strParams);
  
  		return $strUrl;
  	}
docs: Generate a front end URL
  
  @param string $strParams    An optional string of URL parameters
  @param string $strForceLang Force a certain language
  
  @return string An URL that can be used in the front end