dimarti/semaphore

Simple PHP Semaphore

v1.0.0 2024-06-11 08:31 UTC

MIT

• Diego Martínez

Published on Packagist.org on 2024-11-25 17:53 UTC

README

A simple, dependency-free PHP semaphore based on a lock file.

Use it to prevent concurrent execution of a script — for example, to stop a cron job from overlapping with a previous run that hasn't finished yet.

Installation

composer require dimarti/semaphore

Requires PHP 7.0+ (uses scalar type hints and void return types).

Usage

use Dimarti\Semaphore\Semaphore;

$semaphore = new Semaphore('/tmp/my-task.lock');

if ($semaphore->isLocked()) {
    exit("Another instance is already running.\n");
}

$semaphore->lock();

try {
    // ... do your work ...
} finally {
    $semaphore->unlock();
}

API

Method	Description
__construct(string $lockfile)	Creates a semaphore bound to the given lock file path.
lock(): void	Creates the lock file and writes the current timestamp (Y-m-d H:i:s) into it.
unlock(): void	Removes the lock file.
isLocked(): bool	Returns true if the lock file exists, false otherwise.

How it works

The lock state is represented by the presence of a single file on disk:

• lock() writes the file (with a timestamp as its contents).
• unlock() deletes the file.
• isLocked() checks whether the file exists.

License

MIT