抽象类传递对象

abstract class Employee{    protected $name;    function __construct($name){        $this->name = $name;    }    abstract function fire();}class Minion extends Employee{    function fire(){        echo $this->name.':i will clear my desk';    }}class NastyBoss{    private $employees = array();    function addEmployee($employeeName){        $this->employees[] = new Minion($employeeName);    }    function projectFails(){        if(count($this->employees)>0){            $emp = array_pop($this->employees);            $emp->fire();        }    }}$boss = new NastyBoss();$boss->addEmployee('harry');$boss->addEmployee('bob');$boss->addEmployee('mary');$boss->projectFails();//会输出：mary:i will clear my desk