本文实例讲述了PHP使用flock实现文件加锁的方法。分享给大家供大家参考。具体分析如下:
flock在官方文档里的解释是:flock() 允许你执行一个简单的可以在任何平台中使用的读取/写入模型(包括大部分的 Unix 派生版和甚至是Windows)。如果锁定会堵塞的话(EWOULDBLOCK 错误码情况下),请将可选的第三个参数设置为 TRUE。锁定操作也可以被 fclose() 释放(代码执行完毕时也会自动调用)。
简单来说,就是对一个文件进行锁定操作,使得多进程访问该文件时受到限制,从而防止冲突。举个例子:
<?php $file = fopen("test.txt","w+"); if (flock($file,LOCK_EX)) { fwrite($file,"Write something"); flock($file,LOCK_UN); } else { echo "Error locking file!"; } fclose($file); ?>
说明:
1.这段代码的意思是,以读写方式打开文件test.txt,当一个用户调用该php页面时,即对test.txt文件进行操作,那么就会执行flock($file,LOCK_EX)代码,即将test.txt文件进行独占锁定(该文件只能由该用户进行读写操作),那么如果有其他新的用户想访问该文件,就会被阻塞,直到前者关闭文件(释放锁定)。
2.如果将代码改成flock($file,LOCK_EX+LOCK_NB)表示锁定时直接返回错误,那么如果有新的用户访问该文件,就会输出“Error locking file!”
3.该函数的语法是flock(file,lock,block),其中file必需。规定要锁定或释放的已打开的文件。lock 必需。规定要使用哪种锁定类型。block可选。若设置为 1 或 true,则当进行锁定时阻挡其他进程。
例如:请写一段PHP代码,确保多个进程同时写入同一个文件成功
function writeData($path, $mode,$data) { $fp = fopen($path, $mode); $retries = 0; $max_retries = 100; do{ if ($retries > 0) { usleep(rand(1, 10000)); } $retries += 1; }while (!flock($fp, LOCK_EX) and $retries<= $max_retries); if ($retries == $max_retries) { return false; } fwrite($fp, "$data\n"); flock($fp, LOCK_UN); fclose($fp); return true; }
希望本文所述对大家的php程序设计有所帮助。

The article explains how to create, implement, and use interfaces in PHP, focusing on their benefits for code organization and maintainability.

The article discusses the differences between crypt() and password_hash() in PHP for password hashing, focusing on their implementation, security, and suitability for modern web applications.

Article discusses preventing Cross-Site Scripting (XSS) in PHP through input validation, output encoding, and using tools like OWASP ESAPI and HTML Purifier.

Autoloading in PHP automatically loads class files when needed, improving performance by reducing memory use and enhancing code organization. Best practices include using PSR-4 and organizing code effectively.

PHP streams unify handling of resources like files, network sockets, and compression formats via a consistent API, abstracting complexity and enhancing code flexibility and efficiency.

The article discusses managing file upload sizes in PHP, focusing on the default limit of 2MB and how to increase it by modifying php.ini settings.

The article discusses nullable types in PHP, introduced in PHP 7.1, allowing variables or parameters to be either a specified type or null. It highlights benefits like improved readability, type safety, and explicit intent, and explains how to declar

The article discusses the differences between unset() and unlink() functions in programming, focusing on their purposes and use cases. Unset() removes variables from memory, while unlink() deletes files from the filesystem. Both are crucial for effec


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

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

Hot Article

Hot Tools

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

Notepad++7.3.1
Easy-to-use and free code editor

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software
