In PHP, the subclass overrides the method of the parent class [parent::method name]. The neutron parent

cannot define functions with the same name in PHP, including functions that cannot be defined again. Methods with the same name are defined in the same class, so there is no method overloading. Methods with the same name as those of the parent class can be defined in the subclass alone, because the methods of the parent class already exist in the subclass, so the methods inherited from the parent class can be overridden in the subclass.

The method of overriding the parent class in a subclass is to overwrite the methods inherited from the parent class in the subclass. Can’t the methods in the parent class be used directly if they are inherited by the subclass? Why do we need to overload it? Because there are some situations that we have to cover. For example, there is a "Bird" class, in which the general method "Fly" for birds is defined. Taking the "ostrich" class as its subclass will inherit the "flying" method, but as soon as the "flying" method in the "ostrich" class is called, the ostrich will fly away. Although ostriches cannot fly, other characteristics have the characteristics of "birds". Therefore, when declaring the "ostrich" class, you can still inherit the "bird" class, but you must add the "bird" class to the "ostrich" class. To rewrite the "flying" method inherited from the class, you need to overload the method in the parent class in the subclass.

In the following example, there is a "speak" method in the declared Person class. After the Student class inherits the Person class, it can directly use the "speak" method. However, the "speak" method in the Person class can only speak its own member attributes, while the Student class extends the Person class and adds several new member attributes. The code looks like this:

<&#63;php
class Person{
protected $name;
protected $sex;
protected $Wage;
function __construct($name="",$sex="男",$age=1){
$this ->name = $name;
$this ->sex = $sex;
$this ->age = $age;
}
//在人類中聲明一個(gè)通用的說話方法，介紹一下自己
function say(){
echo "我的名字：".$this-> name."，性別：".$this ->sex."，年齡：".$this ->age."。<br>"；
}
}
//聲明一個(gè)學(xué)生類，使用extends關(guān)鍵字?jǐn)U展（繼承）person類
class Student extends Person {
private $school; //在學(xué)生類中聲明一個(gè)所在學(xué)校school的成員屬性
//覆蓋父類中的構(gòu)造方法，在參數(shù)列表中添加一個(gè)學(xué)校屬性，用來創(chuàng)建對象并初始化成員屬性
function __construct($name="",$sex="男",$age=1,$school=""){
$this ->name = $name;
$this ->sex = $sex;
$this ->age = $age;
$this ->school = $school;
}
function study(){
echo $this ->name."正在".$this ->school."學(xué)習(xí)<br>";
}
//定義一個(gè)和父類中同名的方法，將父類中的說話方法覆蓋并重寫，多說出所在的學(xué)校名稱
function say(){
echo "我的名字：".$this ->name."，性別：".$this ->sex."，年齡：".$this ->age."，在".$this ->school."學(xué)校上學(xué)<br>";
}
}
$student= new Student("張三","男",20,"edu"); //創(chuàng)建一個(gè)學(xué)生對象，并傳給一個(gè)學(xué)校名稱參數(shù)
$student -> say(); //調(diào)用學(xué)生類中覆蓋父類的說話方法
&#63;> 

The output result after running the modified program is:

My name is: Zhang San, gender: male, my age is: 20, studying in edu school

In PHP, the function of calling the overridden method of the parent class in the overloaded method of the subclass is provided. In this way, in the methods overridden by the subclass, you can continue to use the methods inherited and overridden from the parent class, and then add more new functions as required. The format of the call is to use "parent: method name" to call the overridden method in the parent class in the overloaded method of the subclass. Modify the code in the above example, use "parent::__construct()" in the overridden constructor of the subclass to call the overridden constructor of the parent class, and add an additional member attribute for the newly extended member of the subclass. Initialization code. Use "parent::say()" in the say() method overridden in the subclass to call the overridden say() method in the parent class, and then add the function of outputting the member attributes of the subclass.

The code is as follows:

<&#63;php
class Person{
protected $name;
protected $sex;
protected $Wage;
function __construct($name="",$sex="男",$age=1){
$this ->name = $name;
$this ->sex = $sex;
$this ->age = $age;
}
//在人類中聲明一個(gè)通用的說話方法，介紹一下自己
function say(){
echo "我的名字：".$this-> name."，性別：".$this ->sex."，年齡：".$this ->age."。<br>"；
}
}
//聲明一個(gè)學(xué)生類，使用extends關(guān)鍵字?jǐn)U展（繼承）person類
class Student extends Person {
private $school; //在學(xué)生類中聲明一個(gè)所在學(xué)校school的成員屬性
//覆蓋父類中的構(gòu)造方法，在參數(shù)列表中添加一個(gè)學(xué)校屬性，用來創(chuàng)建對象并初始化成員屬性
function __construct($name="",$sex="男",$age=1,$school=""){
//調(diào)用父類中被覆蓋的構(gòu)造方法，為從父類中集成過來額出行賦初值
parent::__construct($name,$sex,$age);
$this ->school = $school;
}
function study(){
echo $this ->name."正在".$this ->school."學(xué)習(xí)<br>";
}
//定義一個(gè)和父類中同名的方法，將父類中的說話方法覆蓋并重寫，多說出所在的學(xué)校名稱
function say(){
parent::say(); //調(diào)用父類中被本方法覆蓋掉的方法
echo "在".$this ->school."學(xué)校上學(xué)<br>";
}
}
$student= new Student("張三","男",20,"edu"); //創(chuàng)建一個(gè)學(xué)生對象，并傳給一個(gè)學(xué)校名稱參數(shù)
$student -> say(); //調(diào)用學(xué)生類中覆蓋父類的說話方法
&#63;> 

The output result of the above example is the same as the previous example, but in this case it is much simpler to directly call the overridden method in the parent class in the subclass. In addition, when a subclass overrides a method of a parent class, it must be noted that the access permissions of the methods overridden in the subclass must not be lower than the access permissions of the overridden methods of the parent class. For example, if the access permission in the parent class is protected, then the permission of the method overridden in the child class must be protected or public.

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