php unset() destroys single or multiple variables_PHP tutorial-PHP Tutorial-php.cn

Home

Backend Development

PHP Tutorial

php unset() destroys single or multiple variables_PHP tutorial

WBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWB

Jul 13, 2016 pm 05:14 PM

php unset function variable Multiple us yes of Bring your own destroy

The unset function is a function that comes with PHP to destroy variables. We introduced the method of using unset to destroy static variables and global variables. At the same time, we also introduced the method of destroying array variables. Let's see an example below.

Example 1. unset() example

The code is as follows

Copy code

代码如下

复制代码

// 销毁单个变量
unset ($foo);

// 销毁单个数组元素
unset ($bar['quux']);

// 销毁一个以上的变量
unset ($foo1, $foo2, $foo3);
?>

// Destroy a single variable

unset ($foo);

//Destroy a single array element

代码如下

复制代码

function destroy_foo() {
global $foo;
unset($foo);
}

$foo = ‘bar’;
destroy_foo();
echo $foo;
?>

unset ($bar['quux']);

// Destroy more than one variable

unset ($foo1, $foo2, $foo3);

The behavior of unset() in a function will vary depending on the type of variable you want to destroy.

代码如下

复制代码

function foo(&$bar) {
unset($bar);
$bar = “blah”;
}

$bar = ‘something’;
echo “$barn”;

foo($bar);
echo “$barn”;
?>
上边的例子将输出：

something
something

If you unset() a global variable in a function, only the local variable will be destroyed, and the variables in the calling environment will maintain the same value before calling unset().

The code is as follows

Copy code

function destroy_foo() {

global $foo;

代码如下

复制代码

function foo() {
static $b;
$a++;
$b++;
echo "$a---$bn";
unset($a,$b);
var_dump($a);
var_dump($b);
echo "######################n";
}

foo();
foo();
foo();
?>
运行该例子，输出：

1---1
NULL
NULL
#######################
1---2
NULL
NULL
#######################
1---3
NULL
NULL
#######################

unset($foo); } $foo = ‘bar’; destroy_foo(); echo $foo; ?> The above example will output: bar If you unset() a variable passed by reference in a function, only the local variable will be destroyed, and the variables in the calling environment will retain the same value before calling unset().

The code is as follows	Copy code
function foo(&$bar) {<🎜> unset($bar);<🎜> $bar = “blah”;<🎜> }<🎜> <🎜>$bar = ‘something’;<🎜> echo “$barn”;<🎜> <🎜>foo($bar);<🎜> echo “$barn”;<🎜> ?> The above example will output: something something

unset() static variable Strictly speaking, using unset() to destroy a static variable only breaks the reference between the variable name and the variable value. Example:

The code is as follows	Copy code
function foo() {<🎜> static $b;<🎜> $a++;<🎜> $b++;<🎜> echo "$a---$bn";<🎜> unset($a,$b);<🎜> var_dump($a);<🎜> var_dump($b);<🎜> echo "######################n";<🎜> }<🎜> <🎜>foo();<🎜> foo();<🎜> foo();<🎜> ?> Running this example, output: 1---1 NULL NULL ####################### 1---2 NULL NULL ####################### 1---3 NULL NULL #######################

unset() global variable
Like unset() static variables, if you unset() a global variable in a function, only the local variable will be destroyed, and the variables in the calling environment will retain the same value before calling unset().

Try to compare the following two examples:

global $foo;

The code is as follows

代码如下

复制代码

function destroy_foo() {
global $foo;
unset($foo);
}

$foo = 'bar';
destroy_foo();
echo $foo;
?>

function destroy_foo() {
global $foo;
unset($GLOBALS['foo']);
}

$foo = 'bar';
destroy_foo();
echo $foo;
?>

Copy code

function destroy_foo() {

unset($foo);

}

echo $foo;

Running the first example will output: bar , while the second example will not output anything. http://www.bkjia.com/PHPjc/628977.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/628977.htmlTechArticleThe unset function is a function that comes with PHP to destroy variables. We introduced the use of unset to destroy static variables and globals. The variable method can also destroy array variables. Let’s see below...

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

AI-powered app for creating realistic nude photos

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress images for free

Clothoff.io

AI clothes remover

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

Assassin's Creed Shadows: Seashell Riddle Solution

3 weeks ago By DDD

What's New in Windows 11 KB5054979 & How to Fix Update Issues

2 weeks ago By DDD

Where to find the Crane Control Keycard in Atomfall

3 weeks ago By DDD

Saving in R.E.P.O. Explained (And Save Files)

1 months ago By 尊渡假赌尊渡假赌尊渡假赌

Assassin's Creed Shadows - How To Find The Blacksmith And Unlock Weapon And Armour Customisation

4 weeks ago By DDD

Hot Tools

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

Where is the login entrance for gmail email?

7566

CakePHP Tutorial

1386

What is the format of the account name of steam

win11 activation key permanent

nyt connections hints and answers

106

Related knowledge

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

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

7 PHP Functions I Regret I Didn't Know Before Nov 13, 2024 am 09:42 AM

If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op

How do you parse and process HTML/XML in PHP? Feb 07, 2025 am 11:57 AM

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

Explain JSON Web Tokens (JWT) and their use case in PHP APIs. Apr 05, 2025 am 12:04 AM

JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

PHP Program to Count Vowels in a String Feb 07, 2025 pm 12:12 PM

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

Explain late static binding in PHP (static::). Apr 03, 2025 am 12:04 AM

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases? Apr 03, 2025 am 12:03 AM

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.

See all articles