php面向对象中子类中重载父类详解_PHP教程

class Person{

public $name;

public function __construct($name="" ){
$this->name =$name;

}
public function say(){
echo "我叫".$this->name ;
}

}
?>
class Student extends Person{

public $name;

public function __construct($name=""){
$this->name =$name;

}
//这里定义了一个和父类中同名的方法，将父类中的说话方法覆盖并重写
public function say(){
echo "我叫".$this->name ."，今年25岁了" ;
}

}
?>

class Student extends Person{

public $name;
public $age;

public function __construct($name="",$age=25){
$this->name =$name;

$this->age =$age;

}

public function say(){

echo "我叫".$this->name ."，今年".$this->age."岁了" ;

}

}
?>

class Student extends Person{

public $name;

public $age;

public function __construct($name="",$age=25){

parent::__construct($name,$age);

$this->age =$age;
}

public function say(){
parent::say();

echo "，今年".$this->age."岁了" ;

}

}
?>

// 狗有两只眼睛,会汪汪叫,会跑.
class Dog {
protected $eyeNumber =2; //属性
//返回封装属性的方法.
public function getEyeNumber(){
return $this->eyeNumber;
}
//狗会叫
public function yaff(){
return "Dog yaff, wang ..wang ..";
}
//狗会跑
public function run(){
return "Dog run..running ...";
}
}
$dog = new Dog();
echo "dog have ".$dog->getEyeNumber()." eyes.
";
echo $dog->yaff() ."
".$dog->run();
echo "

";
//这是我的小狗叫"狗狗",它很小.不会汪汪叫,只会哼哼哼..
class MyDog extends Dog {
private $name = "狗狗";
public function getName(){
return $this->name;
}
public function yaff(){
return $this->name." yaff, heng...heng ..";
}
}
$myDog = new MyDog();
echo $myDog->getName()." have ".$myDog->getEyeNumber()." eyes.
";
echo $myDog->yaff() ."
".$myDog->run();
?>

程序运行结果：

dog have 2 eyes.
Dog yaff, wang ..wang ..
Dog run..running ...

狗狗 have 2 eyes.
狗狗 yaff, heng...heng ..
Dog run..running ...

// 简化dog类和mydog类,演示重写的访问权限.
class Dog {
protected $eyeNumber =2; //属性
//返回封装属性的方法.
public function getEyeNumber(){
return $this->eyeNumber;
}
}

class MyDog extends Dog {
protected function getEyeNumber(){
return $this->eyeNumber;
}
}
/*
class MyDog extends Dog {
private function getEyeNumber(){
return $this->eyeNumber;
}
}
*/

?>

程序运行结果：
Fatal error: Access level to MyDog::getEyeNumber() must be public (as in class Dog) in E:PHPProjectstest.php on line 15

// 简化dog类和mydog类,演示重写的访问权限.
class Dog {
protected $eyeNumber =2; //属性
//返回封装属性的方法.
public function getEyeNumber(){
return $this->eyeNumber;
}
}

class MyDog extends Dog {
private function getEyeNumber(){
return $this->eyeNumber;
}
}

?>

程序运行结果：

Fatal error: Access level to MyDog::getEyeNumber() must be public (as in class Dog) in E:PHPProjectstest.php on line 15

// 简化dog类和mydog类,演示重写方法的参数.
class Dog {
protected $eyeNumber =2; //属性
//返回封装属性的方法.
public function getEyeNumber(){
return $this->eyeNumber;
}
}
class MyDog extends Dog {
//重写的方法与父类的方法有不同的参数数量.
public function getEyeNumber($eys){
$this->eyeNumber = $eys;
return $this->eyeNumber;
}
}

$myDog = new MyDog();
echo "my dog hava ".$myDog->getEyeNumber(3) ." eyes.";
//啸天犬..哈..
//下面这句会报一个丢失参数的错误.
//echo "my dog hava ".$myDog->getEyeNumber() ." eyes.";
?>

程序运行结果：

my dog hava 3 eyes.

//2-2 / extends1.php
//构造函数继承的问题.
class Animal{
public $legNum = 0;
public function __construct(){
$this->legNum = 4;
echo "I am an animal
";
}
}
class Dog1 extends Animal {
public function __construct(){
$this->legNum = 4;
echo "I am a Dog .
";
}
}
$dog1 = new Dog1();
echo "
";
echo "legNum is ".$dog1->legNum;
/*
实例化子类时.构造函数被调用了.
*/
?>

程序运行结果：

I am a Dog .
legNum is 4