Detailed tutorial on this, self and parent keywords in PHP5_PHP tutorial

First, let’s understand the above three keywords: this, self, parent, which is easier to understand literally, refers to this, self, father, haha, it’s more fun. Let’s establish a few concepts first. These three keywords are respectively Where is it used? Let's briefly explain that this is a pointer to the current object (let's use the pointer in C for now), self is a pointer to the current class, and parent is a pointer to the parent class. We frequently use pointers to describe here because there is no better language to express it. Haha, I didn’t learn Chinese well. -_-#
It’s not very clear yet, so let’s talk about it based on actual examples.
(1) this

Copy code The code is as follows:

class UserName
{
//Define attributes
private $name;
//Define constructor
function __construct($name)
{
$this->name = $ name; //This pointer has been used here
}
//Destructor
function __destruct(){}
//Print user name member function
function printName()
{
                                                                            print(                                                                                                                                                .
//Perform printing
$nameObject->printName(); //Output: heiyeluren
//Second instantiation of the object
$nameObject = new UserName( "PHP" );
//Execute printing
$nameObject->printName(); //Output: PHP
?>


We see that the above classes are used in rows and rows respectively If the this pointer is found, who does this point to at that time? In fact, this determines who it points to when it is instantiated. For example, when the object is instantiated for the first time (line), then this points to the $nameObject object. Then when printing the line, print( $this-> ;name ), then of course "heiyeluren" is output. In the second instance, print( $this->name ) becomes print( $nameObject->name ), so "PHP" is output. Therefore, this is a pointer to the current object instance and does not point to any other object or class.
(2)self
First of all, we have to make it clear that self points to the class itself, that is, self does not point to any instantiated object. Generally, self is used to point to static variables in the class.

Copy code

The code is as follows:

class Counter
{
//Define attributes, including a static variable
private static $firstCount = ;
private $lastCount;
//Constructor function
function __construct()
{ Field operation symbols)
       }                                                                                                                🎜>                                                                                                 🎜> //Instantiate object
$countObject = new Counter();
$countObject->printLastCount(); //Output
?>


We are here Just pay attention to two places, line 1 and line 1. We defined a static variable $firstCount in the second line, with an initial value of operator, then what we call at this time is the static variable $frestCount defined by the class itself. Our static variable has nothing to do with the instance of the following object, it is only related to the class, then if I call the class itself, then we cannot use this To reference, you can use self to reference, because self points to the class itself and has nothing to do with any object instance. In other words, if there are static members in our class, we must also use self to call them.
(3)parent
We know that parent is a pointer to the parent class. Generally, we use parent to call the constructor of the parent class.



Copy code

The code is as follows:


//Base class class Animal { //Attributes of the base class public $name; //Name

//Constructor of the base class

public function __construct($name)
{ ->name = $name;
} }
}
// Derived class
class Person extends Animal class //Person class inherits Animal class
{
public $personSex; / /Gender
public $personAge; //Age
//Constructor of inherited class
function __construct($personSex, $personAge)
{ parent::__construct("heiyeluren") ; //Use parent to call the constructor of the parent class
$this->personSex = $personSex;
personAge = $personAge; 🎜> {
print( $this->name. " is " .$this->personSex. ",this year " .$this->personAge );
} }
}
//Instantiate the Person object
$personObject = new Person( "male", "");
//Perform printing
$personObject->printPerson(); //Output: heiyeluren is male ,this year  
?>  


We pay attention to the following details: member attributes are all public, especially those of the parent class, for inherited classes to access through this. We pay attention to the key point, line: parent::__construct( "heiyeluren" ). At this time, we use parent to call the constructor of the parent class to initialize the parent class, because the members of the parent class are all public, so We can directly use this to call in the inherited class.
Summary:
This is a pointer to an object instance, self is a reference to the class itself, and parent is a reference to the parent class.
Basically, that’s all I know. There must be some misunderstandings. Experts please point them out!

http://www.bkjia.com/PHPjc/318103.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/318103.htmlTechArticleFirst of all, let’s understand the above three keywords: this, self, parent, which are easier to understand literally. Refers to this, myself, father, haha, it’s more fun. Let’s establish a few concepts first. These three keywords are divided into...