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。
下面就是一个用接口模拟多重继承的例子，源代码如下：
?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??.?$_user->getname()?.
; ??} ??//这里的类型提示改成了 teacherinterface类型. ??public?static?functiongetlengthofservice(teacherinterface?$_teacher){ ?echo?age?is??.$_teacher->getlengthofservice()?.
; ??} ?} ?$graduatestudent?=?new?graduatestudent(); ?act::getusername($graduatestudent); ?act::getlengthofservice($graduatestudent); ?//结果正如我们所要的,实现了有多重身份的一个对象. ??>?
示例运行结果如下：
name is tom
age is 5