Home php教程 php手册 深入理解PHP中的i++和++i的区别

深入理解PHP中的i++和++i的区别

Jun 13, 2016 am 10:15 AM
php

这篇文章主要介绍了浅析PHP中的i++与++i的区别及效率 的相关资料,非常不错具有参考借鉴价值,需要的朋友可以参考下

先看看基本区别:

i++ :先在i所在的表达式中使用i的当前值,后让i加1

++i :让i先加1,然后在i所在的表达式中使用i的新值

看一些视频教程里面写for循环的时候都是写 ++i 而不是 i++,上网搜索了一下,原来有效率问题

++i相当于下列代码

i += 1; 
return i;
Copy after login

i++相当于下列代码

j = i; 
i += 1; 
return j;
Copy after login

当然如果编译器会将这些差别都优化掉,那么效率就都差不多了。

再给大家详细说下++i 与 i++ 的区别

1、++i 的用法(以 a=++i ,i=2 为例)

先将 i 值加 1 (也就是 i=i+1 ),然后赋给变量 a (也就是 a=i ),

则最终 a 值等于 3 , i 值等于 3 。

所以 a=++i 相当于 i=i+1 ,a=i

2、i++ 的用法(以 a=i++ ,i=2 为例)

先将 i 值赋给变量 a (也就是 a=i ),然后 i 值加 1 (也就是 i=i+1 ),

则最终 a 值等于 2 ,i 值等于 3 。

所以 a=i++ 相当于 a=i , i=i+1

3、++i 与 i++

a=++i 相当于 i++ , a=i

a=i++ 相当于 a=i , i++

4、++i 与 i++ 单独使用时,相当于 i=i+1

如果赋给一个新变量,则 ++i 先将 i 值加 1 ,而 i++ 先将 i 赋给新变量。

以上所述是小编给大家介绍的PHP中的i++与++i的区别及效率的全部叙述,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。

更多相关教程请访问  php编程从入门到精通全套视频教程

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
Hello Kitty Island Adventure: How To Get Giant Seeds
1 months ago By 尊渡假赌尊渡假赌尊渡假赌
Two Point Museum: All Exhibits And Where To Find Them
1 months 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

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.

CakePHP Working with Database CakePHP Working with Database Sep 10, 2024 pm 05:25 PM

Working with database in CakePHP is very easy. We will understand the CRUD (Create, Read, Update, Delete) operations in this chapter.

See all articles