core-bundle/src/Resources/contao/library/Contao/Idna.php
public static function encodeUrl($strUrl)
	{
		if ($strUrl == '')
		{
			return '';
		}

		// Empty anchor (see #3555) or insert tag
		if ($strUrl == '#' || strncmp($strUrl, '{{', 2) === 0)
		{
			return $strUrl;
		}

		// E-mail address
		if (strncmp($strUrl, 'mailto:', 7) === 0)
		{
			return static::encodeEmail($strUrl);
		}

		$arrUrl = parse_url($strUrl);

		if (!isset($arrUrl['scheme']))
		{
			throw new \InvalidArgumentException(sprintf('Expected a FQDN, got "%s"', $strUrl));
		}

		// Scheme
		if (isset($arrUrl['scheme']))
		{
			$arrUrl['scheme'] .= ((substr($strUrl, \strlen($arrUrl['scheme']), 3) == '://') ? '://' : ':');
		}

		// User
		if (isset($arrUrl['user']))
		{
			$arrUrl['user'] .= isset($arrUrl['pass']) ? ':' : '@';
		}

		// Password
		if (isset($arrUrl['pass']))
		{
			$arrUrl['pass'] .= '@';
		}

		// Host
		if (isset($arrUrl['host']))
		{
			$arrUrl['host'] = static::encode($arrUrl['host']);
		}

		// Port
		if (isset($arrUrl['port']))
		{
			$arrUrl['port'] = ':' . $arrUrl['port'];
		}

		// Path does not have to be altered

		// Query
		if (isset($arrUrl['query']))
		{
			$arrUrl['query'] = '?' . $arrUrl['query'];
		}

		// Anchor
		if (isset($arrUrl['fragment']))
		{
			$arrUrl['fragment'] = '#' . $arrUrl['fragment'];
		}

		$strReturn = '';

		foreach (array('scheme', 'user', 'pass', 'host', 'port', 'path', 'query', 'fragment') as $key)
		{
			if (isset($arrUrl[$key]))
			{
				$strReturn .= $arrUrl[$key];
			}
		}

		return $strReturn;
	}
public static function encodeUrl($strUrl)
	{
		if ($strUrl == '')
		{
			return '';
		}

		// Empty anchor (see #3555) or insert tag
		if ($strUrl == '#' || strncmp($strUrl, '{{', 2) === 0)
		{
			return $strUrl;
		}

		// E-mail address
		if (strncmp($strUrl, 'mailto:', 7) === 0)
		{
			return static::encodeEmail($strUrl);
		}

		$arrUrl = parse_url($strUrl);

		if (!isset($arrUrl['scheme']))
		{
			throw new \InvalidArgumentException(sprintf('Expected a FQDN, got "%s"', $strUrl));
		}

		// Scheme
		if (isset($arrUrl['scheme']))
		{
			$arrUrl['scheme'] .= ((substr($strUrl, \strlen($arrUrl['scheme']), 3) == '://') ? '://' : ':');
		}

		// User
		if (isset($arrUrl['user']))
		{
			$arrUrl['user'] .= isset($arrUrl['pass']) ? ':' : '@';
		}

		// Password
		if (isset($arrUrl['pass']))
		{
			$arrUrl['pass'] .= '@';
		}

		// Host
		if (isset($arrUrl['host']))
		{
			$arrUrl['host'] = static::encode($arrUrl['host']);
		}

		// Port
		if (isset($arrUrl['port']))
		{
			$arrUrl['port'] = ':' . $arrUrl['port'];
		}

		// Path does not have to be altered

		// Query
		if (isset($arrUrl['query']))
		{
			$arrUrl['query'] = '?' . $arrUrl['query'];
		}

		// Anchor
		if (isset($arrUrl['fragment']))
		{
			$arrUrl['fragment'] = '#' . $arrUrl['fragment'];
		}

		$strReturn = '';

		foreach (array('scheme', 'user', 'pass', 'host', 'port', 'path', 'query', 'fragment') as $key)
		{
			if (isset($arrUrl[$key]))
			{
				$strReturn .= $arrUrl[$key];
			}
		}

		return $strReturn;
	}
Encode the domain in an URL

@param string $strUrl The URL

@return string The encoded URL

@throws \InvalidArgumentException