WsdlToPhp\PackageGenerator\Model\AbstractModel::cleanString PHP Method

    public static function cleanString($string, $keepMultipleUnderscores = true)
    {
        return GeneratorUtils::cleanString($string, $keepMultipleUnderscores);
    }

 /**
  * @param string $name
  * @return string
  */
 protected function getParameterName($name)
 {
     return lcfirst(AbstractModel::cleanString($name));
 }