PHP will call this function as destructor before the object is destroyed.

-Constructors and destructors

If you declare a function in a class named construct, the function will be treated as a constructor and executed when an object instance is created. Clearly, it is two underscores. Just like any other function, Constructors may have parameters or default values. You can define a class to create an object and put its properties all in a single statement (statement).

You can also define a function named Destruct, which will be called by PHP before the object is destroyed. It is called a destructor.

Inheritance is a powerful feature of classes. A class (subclass/derived class) can inherit the functionality of another class (parent class/base class). A derived class will contain all the properties and methods of the base class, and other properties and methods can be added to the derived class. You can also override the methods and properties of the base class. As shown in 3.1.2, You can use the extends keyword to inherit a class.

You might want to know how constructors are inherited. When they are inherited with other methods, they are not executed when the object is created.

If you need this feature, you need to use the following:: operator. It allows you to point to a block of namespaces. The parent points to the parental namespace, and you can use Parent::construct to call the parent class's constructor.

Some object-oriented languages name constructors after the class. This is true for the first few versions of PHP, which is still valid. That is: If you name a class animal and create a name in it, it is also animal. This method is the constructor. If a class has both the Construt constructor and the same function as the class name, PHP will treat construct as a constructor. This makes the classes written in the previous PHP version still available. But the new script (PHP5) construct should be used.

This new method of declaring constructors in PHP allows constructors to have a unique name, regardless of the name of the class in which it resides. So when you change the name of a class, you don't need to change the name of the constructor.

You might give constructors a way to access the constructor in PHP just like any other class method. Access will affect the ability to instantiate objects from within a range. This allows for the implementation of some fixed design patterns, such as singleton mode.

destructor, as opposed to a constructor function. PHP calls them to destroy an object from memory. By default, PHP simply frees the memory occupied by the object's properties and destroys the object-related resources. Destructors allow you to execute arbitrary code after using an object to clear memory.

When PHP decides that your script is no longer related to the object, the destructor is called. Within the namespace of a function, this occurs at the time of the function return. For global variables, this happens at the end of the script. If you want to explicitly destroy an object, You can assign any other value to the variable that points to the object. The variable is usually assigned on duty to null or called unset.

Calculates the number of objects instantiated from a class. The Counter281064151 class adds value from the constructor, reducing the value in the destructor.

Once you have defined a class, you can use new to create an instance of the class. The definition of a class is a design diagram, and an instance is a component placed on an assembly line. New requires the name of the class and returns an instance of the class. If the constructor requires parameters, you should enter the parameters after new.

<?php class Counter {private static$count=0;　　function construct () {self:: $count + +;　　} function destruct () {self:: $count-;　　} function GetCount () {return self:: $count;　　}}//Establish the first instance $c =new Counter (); Output 1 print ($c-&gt;getcount (). "　　&lt;br&gt;n ");　　Establish a second instance $c 2=new Counter (); Output 2 print ($c-&gt;getcount (). "　　&lt;br&gt;n ");　　Destroying instances $c 2=null; Output 1 print ($c-&gt;getcount (). "　　&lt;br&gt;n "); ?>;

When you create a new instance, the memory is prepared to store all the properties. Each instance has its own unique set of properties. However, the method is shared by all instances of the class.