PHP类(四)-类的继承

<?php
	class Person{
		var $name;
		var $age;
		var $sex;
		
		function __construct($name="Alex",$age=12,$sex="Male"){
			$this->name = $name;
			$this->age = $age;
			$this->sex = $sex;
		}
		
		function Say(){
			echo "My name is ".$this->name.",and my age is ".$this->age.",sex is ".$this->sex;
			echo "<br>";
	}
	}
	
	class Student extends Person{
		var $grade;
		
		function Study(){
			echo $this->name." is study in grade ".$this->grade.".And My age is ".$this->age;
			echo "<br>";
		}
	}
	
	class Teacher extends Person{
		var $subject;
		
		function Teach(){
			echo $this->name." teaches ".$this->subject;
			echo "<br>";
		}
	}
	
	$p1 = new Student("John",16,"Male");
	$p1->Say();
	$p1->grade = 8;
	$p1->Study();
	
	$p2 = new Teacher("Tom",23,"Male");
	$p2->Say();
	$p2->subject = "PHP";
	$p2->Teach();
?>