Home Backend Development PHP Tutorial Basic knowledge of PHP: classes and objects (1)_PHP tutorial

Basic knowledge of PHP: classes and objects (1)_PHP tutorial

Jul 21, 2016 pm 03:59 PM
class php and by Keywords Can basic knowledge definition object beginning yes of kind Class name No

Class definition:
starts with the keyword class, followed by the class name, which can be any name that is not a PHP reserved word. Followed by a pair of curly braces, which contains the definition of class members and methods. The

pseudo variable $this
can be used when a method is called inside the object . $this is a reference to the calling object (usually the object the method belongs to, but can also be another object if the method is called statically from within a second object).
//??What is the internal function of static call?
Look at an example:
class A
{
function foo( )
{
if (isset($this)) {
echo '$this is defined (';
echo get_class($this);
echo ")n";
                                                                                                                    echo "$this is not defined.n";
A::foo();
}
}
$a = new A();
$a->foo();
A::foo() ;
$b = new B();
$b->bar();
B::bar();

The output result is:

$this is defined (a)
$this is not defined.
$this is defined (b)
$this is not defined.

/*I wish I knew this I can't understand the specific implementation of the example memory and so on. If anyone can explain it clearly, please let me know. The cow head in our dormitory is hibernating now. When he wakes up, I will ask. */

new

To create an instance of an object, you must create a new object and assign it to a variable. A new object is always assigned a value when it is created, unless the object defines a constructor and an exception is thrown on error.
When assigning an already created instance of an object to a new variable, the new variable will access the same instance as if assigned with the object. This behavior is the same as when passing an instance to a function. You can use cloning to create a new instance of an already created object.

(Although these sentences are short, they may not be easy to understand.)

Examples are as follows:
class SimpleClass
{
// Member declaration
public $var = 'a default value';

// Method declaration
public function displayVar() {
echo $this->var;
}
}

//See the figure below. 1>new instantiates an object in the heap (heap). 2> Point the pointer $instance to him
$instance = new SimpleClass();

//3> Point the pointer $assigned to the instantiated object in the heap
$ assigned = $instance;
//4>Assign the reference (address) of $instance to $reference
$reference =& $instance;

$ instance->var = '$assigned will have this value';$instance = null; // 5> Interrupt the connection between $instance and the instance in the heap.

var_dump($instance);var_dump($reference);
var_dump($assigned);
Output:
NULL
NULLobject(SimpleClass)#1 (1) {
["var"]=>
string(30) "$assigned will have this value"
}

Illustration The whole process:



Class inheritance extends
A class can inherit the methods and members of another class using the extends keyword in the declaration. You cannot extend multiple classes, you can only inherit one base class.

Basic knowledge of PHP: classes and objects (1)_PHP tutorialInherited methods and members can be overridden by redeclaring them with the same name, unless the parent class uses the final keyword when defining the method. Overridden methods or members can be accessed through parent::.

(What is the mechanism of inheritance?)
The source code is as follows:

class ExtendClass extends SimpleClass

{ // Redefine the parent method function displayVar() { echo "Extending classn";
parent::displayVar();
}}
$extended = new ExtendClass();
$extended->displayVar();

Output:

Extending class
a default value


www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/317411.htmlTechArticleClass definition: starts with the keyword class, followed by the class name, which can be any name that is not a PHP reserved word . Followed by a pair of curly braces, which contains the definition of class members and methods. ...
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

CakePHP Project Configuration CakePHP Project Configuration Sep 10, 2024 pm 05:25 PM

In this chapter, we will understand the Environment Variables, General Configuration, Database Configuration and Email Configuration in CakePHP.

PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian Dec 24, 2024 pm 04:42 PM

PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati

CakePHP Date and Time CakePHP Date and Time Sep 10, 2024 pm 05:27 PM

To work with date and time in cakephp4, we are going to make use of the available FrozenTime class.

CakePHP File upload CakePHP File upload Sep 10, 2024 pm 05:27 PM

To work on file upload we are going to use the form helper. Here, is an example for file upload.

CakePHP Routing CakePHP Routing Sep 10, 2024 pm 05:25 PM

In this chapter, we are going to learn the following topics related to routing ?

Discuss CakePHP Discuss CakePHP Sep 10, 2024 pm 05:28 PM

CakePHP is an open-source framework for PHP. It is intended to make developing, deploying and maintaining applications much easier. CakePHP is based on a MVC-like architecture that is both powerful and easy to grasp. Models, Views, and Controllers gu

How To Set Up Visual Studio Code (VS Code) for PHP Development How To Set Up Visual Studio Code (VS Code) for PHP Development Dec 20, 2024 am 11:31 AM

Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c

CakePHP Creating Validators CakePHP Creating Validators Sep 10, 2024 pm 05:26 PM

Validator can be created by adding the following two lines in the controller.

See all articles