core-bundle/src/Resources/contao/library/Contao/Environment.php
protected static function httpHost()
	{
		if (!empty($_SERVER['HTTP_HOST']))
		{
			$host = $_SERVER['HTTP_HOST'];
		}
		else
		{
			$host = $_SERVER['SERVER_NAME'];

			if ($_SERVER['SERVER_PORT'] != 80)
			{
				$host .= ':' . $_SERVER['SERVER_PORT'];
			}
		}

		return preg_replace('/[^A-Za-z0-9[\].:-]/', '', $host);
	}
protected static function httpHost()
	{
		if (!empty($_SERVER['HTTP_HOST']))
		{
			$host = $_SERVER['HTTP_HOST'];
		}
		else
		{
			$host = $_SERVER['SERVER_NAME'];

			if ($_SERVER['SERVER_PORT'] != 80)
			{
				$host .= ':' . $_SERVER['SERVER_PORT'];
			}
		}

		return preg_replace('/[^A-Za-z0-9[\].:-]/', '', $host);
	}
Return the HTTP Host

@return string The host name