PHP 类的继承(extends)
编写了两个文件：person-student.inc和extends.php。
person-student.inc是一个类文件，包含了对一个Person的定义，其中Student类继承了Person类，实现如下所示：
<?php
class Person{
var $id;
var $name;
var $age;
var $email;
function Person($id,$name,$age,$email){
$this->id = $id;
$this->name = $name;
$this->age = $age;
$this->email = $email;
}
function setId($id){
$this->id = $id;
}
function setName($name){
$this->name = $name;
}
function setAge($age){
$this->age = $age;
}
function setEmail($email){
$this->email = $email;
}
function getId(){
return $this->id;
}
function getName(){
return $this->name;
}
function getAge(){
return $this->age;
}
function getEmail(){
return $this->email;
}
function display(){
echo "<B>身份证号：</B>".$this->id."<BR>";
echo "<B>真实姓名：</B>".$this->name."<BR>";
echo "<B>实际年龄：</B>".$this->age."<BR>";
echo "<B>联系邮箱：</B>".$this->email."<BR>";
echo "<BR>";
}
}
class Student extends Person{
var $sno;
var $school;
var $grade;
var $score;
function Student($sno,$name,$school,$grade,$score){
$this->sno = $sno;
$this->name = $name;
$this->school = $school;
$this->grade = $grade;
$this->score = $score;
}
function setSno($sno){
$this->sno = $sno;
}
function setSchool($school){
$this->school = $school;
}
function setGrade($grade){
$this->grade = $grade;
}
function setScore($score){
$this->scorer = $score;
}
function getSno(){
return $this->sno;
}
function getSchool(){
return $this->school;
}
function getGrade(){
return $this->grade;
}
function getScore(){
return $this->score;
}
function display(){
echo "<B>学生个人信息如下：</B><BR><BR>";
parent::display();
echo "<B>学生学号：</B>".$this->sno."<BR>";
echo "<B>所在学校：</B>".$this->school."<BR>";
echo "<B>所在年级：</B>".$this->grade."<BR>";
echo "<B>高考分数：</B>".$this->score."<BR>";
echo "<BR>";
}
function enroll($score){
$flag = floor($score/100);
echo "<B>你的考试录取估计如下：</B><BR>";
switch($flag){
case 7:
case 6:
echo "你的分数为".$score."，好强啊，能够考取一个名牌大学。<BR>";
break;
case 5:
echo "你的分数为".$score."，能够考取一个普通重点大学。<BR>";
break;
case 4:
echo "你的分数为".$score."，能够考取一个普通本科大学。<BR>";
break;
case 3:
echo "你的分数为".$score."，能够考取一个专科大学。<BR>";
break;
default:
echo "你的分数也太低了点，继续努力吧。<BR>";
break;
}
}
}
?>
Student类继承了Person类，继承使用关键字extends；
上面Student类又新增了一些独有的成员变量；
同 时Student类重写了Person类中的同名方法display()方法，在Student类中该方法使用parent关键字调用了基类的 display()方法，调用基类方法使用操作符“::”，当然也可以使用类名来调用(也就是说，parent::display();与 Person::display();是等价的)；
Student类又增加了一个enroll()方法的实现。
测试页面为extends.php，实现如下所示：
<?php
require("person-student.inc");
$student = new Student(2008001,"Shinrdrn","长春28中","高三",666);
$student->setId("2224031983011999x");
$student->setAge(26);
$student->setEmail("");
$student->display();
$student->enroll($student->getScore());
unset($student);
?>
启动Apache服务器，在IE地址栏中键入：
http://localhost/shirdrn/oo/extends.php
浏览页面显示结果如下所示：
上面的实现，是将Person类和Student类写在了同一个类文件中，当然也可以将他们分开，每一个类写在一个单独的类文件中，下面使用两个类文件分别实现Person类和Student。
Person类的实现为person.inc，如下所示：
<?php
class Person{
var $id;
var $name;
var $age;
var $email;
function Person($id,$name,$age,$email){
$this->id = $id;
$this->name = $name;
$this->age = $age;
$this->email = $email;
}
function setId($id){
$this->id = $id;
}
function setName($name){
$this->name = $name;
}
function setAge($age){
$this->age = $age;
}
function setEmail($email){
$this->email = $email;
}
function getId(){
return $this->id;
}
function getName(){
return $this->name;
}
function getAge(){
return $this->age;
}
function getEmail(){
return $this->email;
}
function display(){
echo "<B>身份证号：</B>".$this->id."<BR>";
echo "<B>真实姓名：</B>".$this->name."<BR>";
echo "<B>实际年龄：</B>".$this->age."<BR>";
echo "<B>联系邮箱：</B>".$this->email."<BR>";
echo "<BR>";
}
}
?>
Student类的实现为student.inc，如下所示：
<?php
require("person.inc");
class Student extends Person{
var $sno;
var $school;
var $grade;
var $score;
function Student($sno,$name,$school,$grade,$score){
$this->sno = $sno;
$this->name = $name;
$this->school = $school;
$this->grade = $grade;
$this->score = $score;
}
function setSno($sno){
$this->sno = $sno;
}
function setSchool($school){
$this->school = $school;
}
function setGrade($grade){
$this->grade = $grade;
}
function setScore($score){
$this->scorer = $score;
}
function getSno(){
return $this->sno;
}
function getSchool(){
return $this->school;
}
function getGrade(){
return $this->grade;
}
function getScore(){
return $this->score;
}
function display(){
echo "<B>学生个人信息如下：</B><BR><BR>";
parent::display();
echo "<B>学生学号：</B>".$this->sno."<BR>";
echo "<B>所在学校：</B>".$this->school."<BR>";
echo "<B>所在年级：</B>".$this->grade."<BR>";
echo "<B>高考分数：</B>".$this->score."<BR>";
echo "<BR>";
}
function enroll($score){
$flag = floor($score/100);
echo "<B>你的考试录取估计如下：</B><BR>";
switch($flag){
case 7:
case 6:
echo "你的分数为".$score."，好强啊，能够考取一个名牌大学。<BR>";
break;
case 5:
echo "你的分数为".$score."，能够考取一个普通重点大学。<BR>";
break;
case 4:
echo "你的分数为".$score."，能够考取一个普通本科大学。<BR>";
break;
case 3:
echo "你的分数为".$score."，能够考取一个专科大学。<BR>";
break;
default:
echo "你的分数也太低了点，继续努力吧。<BR>";
break;
}
}
}
?>
测试文件为ext.php，在该文件中使用Student类只需要包含student.inc文件：
require("student.inc");
实现代码如下所示：
<?php
require("student.inc");
$student = new Student(2008001,"Zhangsan","XX重点中学","高三",260);
$student->setId("5004031988011999x");
$student->setAge(22);
$student->setEmail("");
$student->display();
$student->enroll($student->getScore());
unset($student);
?>
启动Apache服务器，在IE地址栏中键入：
http://localhost/shirdrn/oo/ext.php
浏览页面显示结果如下所示：
来源：http://hi.baidu.com/shirdrn/item/19b0a6b152894476254b09a9