/**
  * Method to test an external url for a valid parts.
  *
  * @param   SimpleXMLElement  $element  The SimpleXMLElement object representing the <field /> tag for the form field object.
  * @param   mixed             $value    The form field value to validate.
  * @param   string            $group    The field name group control value. This acts as as an array container for the field.
  *                                      For example if the field has name="foo" and the group value is set to "bar" then the
  *                                      full field name would end up being "bar[foo]".
  * @param   JRegistry         $input    An optional JRegistry object with the entire data set to validate against the entire form.
  * @param   JForm             $form     The form object for which the field is being tested.
  *
  * @return  boolean  True if the value is valid, false otherwise.
  *
  * @since   11.1
  * @link    http://www.w3.org/Addressing/URL/url-spec.txt
  * @see	    Jstring
  */
 public function test(SimpleXMLElement $element, $value, $group = null, Registry $input = null, Form $form = null)
 {
     // If the field is empty and not required, the field is valid.
     $required = (string) $element['required'] == 'true' || (string) $element['required'] == 'required';
     if (!$required && empty($value)) {
         return true;
     }
     $urlParts = String::parse_url($value);
     // See http://www.w3.org/Addressing/URL/url-spec.txt
     // Use the full list or optionally specify a list of permitted schemes.
     if ($element['schemes'] == '') {
         $scheme = array('http', 'https', 'ftp', 'ftps', 'gopher', 'mailto', 'news', 'prospero', 'telnet', 'rlogin', 'tn3270', 'wais', 'url', 'mid', 'cid', 'nntp', 'tel', 'urn', 'ldap', 'file', 'fax', 'modem', 'git');
     } else {
         $scheme = explode(',', $element['schemes']);
     }
     /*
      * This rule is only for full URLs with schemes because parse_url does not parse
      * accurately without a scheme.
      * @see http://php.net/manual/en/function.parse-url.php
      */
     if ($urlParts && !array_key_exists('scheme', $urlParts)) {
         return false;
     }
     $urlScheme = (string) $urlParts['scheme'];
     $urlScheme = strtolower($urlScheme);
     if (in_array($urlScheme, $scheme) == false) {
         return false;
     }
     // For some schemes here must be two slashes.
     if (($urlScheme == 'http' || $urlScheme == 'https' || $urlScheme == 'ftp' || $urlScheme == 'sftp' || $urlScheme == 'gopher' || $urlScheme == 'wais' || $urlScheme == 'gopher' || $urlScheme == 'prospero' || $urlScheme == 'telnet' || $urlScheme == 'git') && substr($value, strlen($urlScheme), 3) !== '://') {
         return false;
     }
     // The best we can do for the rest is make sure that the strings are valid UTF-8
     // and the port is an integer.
     if (array_key_exists('host', $urlParts) && !String::valid((string) $urlParts['host'])) {
         return false;
     }
     if (array_key_exists('port', $urlParts) && !is_int((int) $urlParts['port'])) {
         return false;
     }
     if (array_key_exists('path', $urlParts) && !String::valid((string) $urlParts['path'])) {
         return false;
     }
     return true;
 }