Home Backend Development PHP Tutorial PHP flock file lock_PHP tutorial

PHP flock file lock_PHP tutorial

Jul 13, 2016 pm 05:45 PM
flock php superior introduce function document usage of Lock locking

//Introduction to flock function usage on w3school:
PHP flock() function

Definition and Usage

The flock() function locks or releases a file.

If successful, returns true. On failure, returns false.

Grammar
flock(file,lock,block)
Parameter Description
file required. Specifies an open file to be locked or released.
lock required. Specifies which lock type to use.
block is optional. If set to 1 or true, blocks other processes while locking.
Description
The file used by flock() must be an open file pointer.

The lock parameter can be one of the following values:

To obtain a shared lock (reading program), set lock to LOCK_SH (set to 1 in versions prior to PHP 4.0.1).
To obtain an exclusive lock (writing program), set lock to LOCK_EX (set to 2 in versions prior to PHP 4.0.1).
To release a lock (whether shared or exclusive), set lock to LOCK_UN (set to 3 in versions prior to PHP 4.0.1).
If you do not want flock() to block on lock, add LOCK_NB to lock (set to 4 in versions prior to PHP 4.0.1).
Tips and Notes

Tip: The lock operation can be released through fclose(), which will be automatically called when the code is completed.

Note: Since flock() requires a file pointer, you may have to use a special lock file to protect access to files intended to be opened in write mode (adding "w" or "w+" to the fopen() function).

Example


==================================================
From: http://hxsdit.com/1110
PHP comes with a file lock function:
bool flock ( int $handle , int $operation [, int &$wouldblock ] )
$handle is the open file pointer;
$operation can be
"LOCK_SH", shared lock; "LOCK_EX", exclusive lock; "LOCK_UN", releases the lock; "LOCK_NB", prevents blocking when flock is locked.
Here we mainly talk about "LOCK_EX" and "LOCK_NB".
For example, we have two files, as follows.
flocka.php

?View Code PHP
1 2 3 4 5 6 7 8 9 10
$file = 'temp.txt'; $fp = fopen($file,'a'); for($i = 0;$i < 5;$i++) { fwrite($fp, "11111111n"); sleep (1); } fclose($fp);

flockb.php

?View Code PHP
1 2 3 4 5 6 7 8 9
$file = 'temp.txt'; $fp = fopen($file,'a'); for($i = 0;$i < 5;$i++) { fwrite($fp, "22222222n"); } fclose($fp);
Run flocka.php first, then flockb.php immediately.
Result:
11111111
22222222
22222222
22222222
22222222
22222222
11111111
11111111
11111111
11111111
Note that when no file lock is added, the two files will write to the txt file at the same time.
Let’s modify the code of the two php files.
flocka.php

?View Code PHP
1 2 3 4 5 6 7 8 9 10 11 12 13
$file = 'temp.txt'; $fp = fopen($file,'a'); if(flock($fp,LOCK_EX)) { for($i = 0;$i < 5;$i++) { fwrite($fp, "11111111n");                   sleep(1);                          flock($fp,LOCK_UN); flockb.php

?View Code PHP
1 2 3 4 5 6 7 8 9 10 11 12 13
$file = 'temp.txt'; $fp = fopen($file,'a'); if(flock($fp,LOCK_EX)) { for($i = 0;$i < 5;$i++) { fwrite($fp, "22222222n"); } } flock($fp,LOCK_UN); } fclose($fp);
Also run flocka.php first, and then flockb.php immediately.
You will find that flockb.php is in a waiting state before flocka.php finishes running. Only when flocka.php finishes running, flockb.php will continue to execute.
Output result:
11111111
11111111
11111111
11111111
11111111
22222222
22222222
22222222
22222222
22222222
In addition, when flock is executed, the file lock is automatically released.

www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/478698.htmlTechArticle//W3school’s introduction to flock function usage: PHP flock() function definition and usage flock() function Lock or release files. If successful, returns true. On failure, returns false. ...
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

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

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)

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

7 PHP Functions I Regret I Didn't Know Before 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 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

Explain JSON Web Tokens (JWT) and their use case in PHP APIs. 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 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

How do you parse and process HTML/XML in PHP? 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 late static binding in PHP (static::). 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? 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