Detailed explanation of flock file lock in php
Remarks: 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). Note: flock() cannot be used with NFS and some other network file systems. Check your operating system's documentation for details. On some operating systems flock() is implemented at the process level. When using a multi-threaded server API (such as ISAPI), it may not be possible to rely on flock() to protect the file, because the file can be processed by PHP scripts running in other parallel threads in the same server instance. flock() does not support older file systems such as FAT and its derivatives. Therefore, FALSE is always returned in this environment (especially for Windows 98 users). Introduction to the usage of the file lock function flock function in php: Syntax: bool flock ( int $handle , int $operation [, int &$wouldblock ] ) The handle of the flock() operation must be an open file pointer. operation can be one of the following values: 1. To obtain a shared lock (reader), set operation to LOCK_SH (set to 1 in versions prior to PHP 4.0.1) 2. To obtain an exclusive lock (writer), set operation to LOCK_EX (set to 2 in versions prior to PHP 4.0.1) 3. To release the lock (whether shared or exclusive), set operation to LOCK_UN (set to 3 in versions prior to PHP 4.0.1) 4. If you don’t want flock() to block when locked, add LOCK_NB to the operation (set to 4 in versions prior to PHP 4.0.1) Look at the code below. File: a.php
file: b.php
After running a.php, run b.php immediately and you can see the output: abc After a.php has finished running, run b.php and you can see the output: abc 123 Obviously, when a.php writes the file, the data is too large and takes a long time. At this time, b.php reads the data incompletely and makes modifications to b.php. Modify b.php to:
After running a.php, run b.php immediately. You can find that b.php will wait until a.php is completed (that is, after 10 seconds) before displaying: abc 123 The read data is complete, but the time is too long. He has to wait for the write lock to be released before making modifications to b.php. Modify b.php to:
After running a.php, run b.php immediately and you can see the output: Lock file failed… It is proved that the lock file failure status can be returned instead of waiting for a long time as above. Script House editor’s conclusion: It is recommended to select relevant locks when caching files, otherwise the read data may be incomplete or the data may be written repeatedly. It seems that file_get_contents cannot select the lock. I don’t know what lock it uses by default. Anyway, the output obtained by not locking is the same as incomplete data. |

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

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

Alipay PHP...

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,

Session hijacking can be achieved through the following steps: 1. Obtain the session ID, 2. Use the session ID, 3. Keep the session active. The methods to prevent session hijacking in PHP include: 1. Use the session_regenerate_id() function to regenerate the session ID, 2. Store session data through the database, 3. Ensure that all session data is transmitted through HTTPS.

The application of SOLID principle in PHP development includes: 1. Single responsibility principle (SRP): Each class is responsible for only one function. 2. Open and close principle (OCP): Changes are achieved through extension rather than modification. 3. Lisch's Substitution Principle (LSP): Subclasses can replace base classes without affecting program accuracy. 4. Interface isolation principle (ISP): Use fine-grained interfaces to avoid dependencies and unused methods. 5. Dependency inversion principle (DIP): High and low-level modules rely on abstraction and are implemented through dependency injection.

The enumeration function in PHP8.1 enhances the clarity and type safety of the code by defining named constants. 1) Enumerations can be integers, strings or objects, improving code readability and type safety. 2) Enumeration is based on class and supports object-oriented features such as traversal and reflection. 3) Enumeration can be used for comparison and assignment to ensure type safety. 4) Enumeration supports adding methods to implement complex logic. 5) Strict type checking and error handling can avoid common errors. 6) Enumeration reduces magic value and improves maintainability, but pay attention to performance optimization.

How to debug CLI mode in PHPStorm? When developing with PHPStorm, sometimes we need to debug PHP in command line interface (CLI) mode...

How to automatically set the permissions of unixsocket after the system restarts. Every time the system restarts, we need to execute the following command to modify the permissions of unixsocket: sudo...

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.
