php接口实现多重继承的例子

php类虽然是单继承的，但是可以通过其它特殊的方式实现多重继承，比如使用接口实现，只要把类的特征抽象为接口，并通过实现接口的方式让对象有多重身份，通过这样就可以模拟多重继承了。

例子，用接口模拟多重继承。
 

<?php
interface UserInterface{ //定义User的接口  
 function getname();  
}  
interface TeacherInterface{ //teacher相关接口  
 function getLengthOfService();  
}  
class User implements UserInterface { //实现UserInterface接口  
 private $name = "tom";  
 public function getName(){  
  return $this->name;  
 }  
}  
class Teacher implements TeacherInterface { //实现TeacherInterface接口  
 private $lengthOfService = 5; // 工龄   
 public function getLengthOfService(){  
  return $this->lengthOfService;  
 }  
}  
// 继承自User类,同时实现了TeacherInterface接口.  
class GraduateStudent extends User implements TeacherInterface {  
 private $teacher ;  
 public function __construct(){  
  $this->teacher = new Teacher();    
 }   
 public function getLengthOfService(){  
  return $this->teacher->getLengthOfService();  
 }  
}  
class Act{  
 //注意这里的类型提示改成了接口类型  
 public static function getUserName(UserInterface $_user){  
  echo "Name is " . $_user->getName() ."<br>";  
 }  
 //这里的类型提示改成了TeacherInterface类型.  
 public static function  getLengthOfService(TeacherInterface $_teacher){  
  echo "Age is " .$_teacher->getLengthOfService() ."<br>";  
 }  
}  
$graduateStudent = new GraduateStudent();  
Act::getUserName($graduateStudent);  
Act::getLengthOfService($graduateStudent);  
//实现了有多重身份的一个对象.  
?> 

结果：
Name is tom
Age is 5