class test{
 public static function test(){
  self::func();

  static::func();
 }

 public static function func(){}
}

class Car
{
 public static function model(){
  self::getModel();
 }

 protected static function getModel(){
  echo "This is a car model";
 }
}

Class Taxi extends Car
{
 protected static function getModel(){
  echo "This is a Taxi model";
 }
}

This is a car model
This is a car model

class Car
{
 public static function model(){
  static::getModel();
 }

 protected static function getModel(){
  echo "This is a car model";
 }
}

Car::model();

Class Taxi extends Car
{
 protected static function getModel(){
  echo "This is a Taxi model";
 }
}

Taxi::model();

This is a car model
This is a Taxi model