protected function validate_street_address($field, $input, $param = null)
    {
        if (!isset($input[$field]) || empty($input[$field])) {
            return;
        }

        // Theory: 1 number, 1 or more spaces, 1 or more words
        $hasLetter = preg_match('/[a-zA-Z]/', $input[$field]);
        $hasDigit = preg_match('/\d/', $input[$field]);
        $hasSpace = preg_match('/\s/', $input[$field]);

        $passes = $hasLetter && $hasDigit && $hasSpace;

        if (!$passes) {
            return array(
                'field' => $field,
                'value' => $input[$field],
                'rule' => __FUNCTION__,
                'param' => $param,
            );
        }
    }