Detailed explanation of magic methods commonly used in PHP

This article mainly introduces relevant information about magic methods commonly used in PHP. Has very good reference value. Let's take a look at it with the editor

We often use magic methods in PHP, such as construction methods, destructor methods and other magic variables. Here is a summary of some commonly used magic variables:

__construct(),__destruct(),__clone(),__autoload(),__tostring(),__invoke(),__set(),__get(),__unset(),__isset(),__call( ),__callstatic;

1,__constuct() constructor

Usually after instantiating an object, the properties of the object must be Initialize! When instantiating an object, the PHP system will automatically call a method named __construct(). We call this method the "constructor method"!

Among them, the constructor can have no parameters!

<?php

class Stu {

 public $stu_name;
 public $stu_age;

//构造方法，实例化时自动调用
 public function __construct($name,$age){

  $this->stu_name = $name;
  $this->stu_age = $age;
 } 

}

//实例化stu对象
$stu = new Stu(&#39;孙悟空&#39;,&#39;500&#39;);

2.__destruct() The destructor method

is a pair with the construction method, and the construction method is The system automatically calls an object when it is "born", and the destructor method is automatically called by the system when an object "disappears"!

The name of the destructor method is __destruct(); note that there cannot be any parameters in it!

<?php

//析构方法
public function __destruct(){

}
?>

Note: The destructor method is called before the object is destroyed!

Function:

The destructor method is generally used to release additional resources occupied by the object. , instead of destroying the object itself!

3, __clone() cloning

Trigger timing: It is the work of initializing the new object when cloning an object

//克隆方法在克隆对象的时候对新对象的初始化工作
 
public function __clone(){
 
 $this->is_clone=true;
}　

Thinking:

Is the cloned object still an instance of the Student class? ?

We can use the instanceof operator to make judgments!

instanceof is used to determine whether an object is an instance of a certain class!

Requires two operands, the front is an object variable, and the back is a class name! Return a boolean value!

var_dump($stu instanceof Stu); //Return bool (true)

4.__autoload() automatically loads the class

Automatically called when calling a non-existent class!

<?php 

/**
* 自动加载类
* 需要什么类__autoload会自动调用需要的文件
*
*/

public function __autoload($class_name)
{
 require_once "../Model/{$class_name}.class.php";
}
 ?>

5.__tostring()

Automatically called when the object is used as a string

6.__invoke()

Automatically called when the object is used as a function

7,__set()

Automatically called when assigning a value to an inaccessible property (for example: calling a private property outside the class)

8.__get()

When the acquisition is inaccessible Automatically called when the attribute value

9.__unset()

Automatically called when the inaccessible attribute is destroyed

10 .__isset()

Automatically called when judging whether the inaccessible attribute exists

11.__call()

When called Automatically triggered when ordinary methods cannot be accessed

<?php 
class Stu{

 public function __call(){
　　　　echo "error";
 }
}
$stu = new Stu();
//此时Stu类里没有show()方法，会触发__call()函数
$stu->show();

12.__callststic()

When cannot be accessed through static methods Automatically trigger when

<?php 
class Stu{

 public static function __callstatic(){
  echo "error";
 }
}
$stu = new Stu();
//此时Stu类里没有show()方法，会触发__call()函数
$stu::show();

The above is the entire content of this article, I hope it will be helpful to everyone's learning.

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