Home php教程 PHP源码 Explanation of strange phenomena in PHP character variables

Explanation of strange phenomena in PHP character variables

Jul 06, 2016 pm 01:34 PM
dump echo nbsp php quot

Sometimes PHP character variables are not executed according to our ideas when used. Regarding this problem, the editor will compile a tutorial for you. Let’s look at the explanation of the strange phenomenon of PHP character variables, as follows.

First of all, the magical PHP supports character data types. Some students wrote this piece of code:


for ($c = 'a'; $c <= 'z'; $c ) {
echo $c . ' ';

}


However, the result was not what he wanted from a to z
a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai
aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd be bf bg bh
bi bj bk bl bm bn bo bp bq br bs bt bu bv bw bx by bz ca cb cc cd ce cf cg
ch ci cj ck cl cm cn co cp cq cr cs ct cu cv cw cx cy cz da db dc dd de df
dg dh di dj dk dl dm dn do dp dq dr ds dt du dv dw dx dy dz ea eb ec ed ee

ef eg eh ei ej ek el em en eo ep eq er es et eu ev ew ex... on to yz


There are many ways to print from a to z, such as the following
for ($i = 'a'; $i != 'aa'; $i )
echo $i . ' ';


for ($i = ord('a'); $i <= ord('z'); $i )
echo chr($i) . ' ';

echo implode(' ', range('a', 'z'));


But we still have to explain what the hell is that bunch printed above?
This is because PHP follows Perl's usage rather than C's when dealing with arithmetic operations on single character variables.
In Perl
$a = 'Z';

$a; //'AA'


In C
a = 'Z';

a ; //'[' Because the ASCII value of 'Z' is 90, the ASCII value of '[' is 91


Note that character variables can only be incremented, not decremented, and only support pure letters (a-z and A-Z), as shown below:
$a="9F9";
$b="9F9";
var_dump( $a); //"9G0"

var_dump(--$b); //"9F9" unchanged


Then some students who wrote like this cried
$a = "9E0";
var_dump( $a); // float(10)

#This TM has become scientific notation again. . .

PHP never follows the rules! <script>ec(2);</script>
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