abstract function continueToWork();
class Sales extends Employee{
private function makeSalePlan(){
public function continueToWork(){
class Market extends Employee{
private function makeProductPrice(){
echo "make product price";
public function continueToWork(){
$this->makeProductPrice();
class Engineer extends Employee{
private function makeNewProduct(){
public function continueToWork(){
public function Work(Employee $employeeObj){//添加父类类型限制传参类型,使其满足多态第三点要求,父类指向子类
$employeeObj->continueToWork();
$obj->Work(new Market());
$obj->Work(new Engineer());