Summary of several magic method syntax and usage examples in php

Commonly used magic methods are: Tostring () Call() autoLoad() clone() GET() SET() isset() unset()

1.Tostring() Used to define the output object Called when referencing Often used to print information about some objects must have a return value
eg: There is a persion class
Persion per =new persion()
Echo per; //Direct call will cause an error
We can add the tostring() method in the definition of the class

Function  Tostring()
{
$str=this->$name.this->age;
Return $str;
}

2.Clone() object copy
Reference assignment
$per1=$per2; And this has only one address in the memory
And $per1=clone $per2 This There are two memory addresses at the time

3. The call() method is automatically executed when calling a function that does not exist in the class instance
If you try to call a function that does not exist in the class, it will A syntax error occurs. In order to provide a friendly prompt
, we can declare the Call() method in the class;

Function call($funName,$argu)
{
Echo "名为".$funName."参数为".printf($argh)."的函数不存在",
}

4.autoLoad Automatic loading Class file used This function is to add
to the referenced page. We have all used this situation. When we need to call other php files in the page, we need to use the include method
but if There are dozens of pages that need to be referenced, which is too cumbersome. We can use the autoload method

Function autoload($className)
{
Include $className.".php";
}

on this page. In this way, wherever other classes are referenced, this class file will be automatically referenced. The name of the prerequisite class file must be Yes Class name.php

5.GET() Access private properties in the class
If the properties in the class are set to private properties, they cannot be accessed in the instance of the class. But how to access it?
We can use GET()
Eg:
There is

class person
{
Private $name;
Private $age;
}

in the class to instantiate person per=new person()
Per-> $name; //The value cannot be obtained in this way
But if we add the GET method in the class

Function GET($proName)
{
Return this->$proName;
}

We can access it by calling Per->$name again
Does anyone do this You may ask, what is the difference between directly accessing private variables and declaring them public?
If it is declared public, we can read it arbitrarily. If it is private, if we add the get method, then the content of the GET method will be called every time the private attribute is called, so we can add some logic to the get method. deal with.

6.SET() sets private properties in the class
The principle is the same as above. We can add the SET() function to the class and assign a value to the private property by calling the class instance. , will execute the SET function, Function prototype:

Function SET($proName,$value)
{
This->$proName=$value;
}

Since it is a method assignment, we can do some logical processing

7.isset() Judgment Class Automatically call
when private properties or methods exist in First, let’s introduce the isset method. This method is used to determine whether
properties and methods
exist, but we cannot determine the class through the class instance. Does a private attribute in exist?If we use isset(per->$name);//The return value is false, but the $name attribute does exist, how to solve it?
Solution:
1. Define $name as a private property

2. Add

Function isset($proName)
{
Return  isset（this->$proName）;//再类内部是可以访问私有属性的
}

in the class definition

In this case, we call isset($name) again; the return value will be true;
8.unset() is automatically called when clearing private variables in the class

and The combination is unset(). The unset method can delete attributes. When we need to delete attributes in a class, if it is a public attribute, we can directly

delete it, but if it is private, we cannot achieve it through this method only.

How to implement it? We can use the unset() method to achieve this function. We need to add

Function unset($proName){Unset(this->$proName);}

Now we call unset($name); to delete the private attribute $name in the person class# #####

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