使用PHP同步功能 [英] Synchronized functions using PHP
问题描述
如何使PHP中的函数同步,以使相同的函数不会被同时执行?第二位用户必须等到第一位用户完成此功能.然后第二个用户可以执行该功能.
How to make functions in PHP synchronized so that same function won't be executed concurrently ? 2nd user must wait till 1st user is done with the function. Then 2nd user can execute the function.
谢谢
推荐答案
这基本上归结为在功能已锁定且无法执行,直到第一个调用者从该函数返回之前执行的位置设置标志. 这可以通过多种方式完成:
This basically comes down to setting a flag somewhere that the function is locked and cannot be executed until the first caller returns from that function. This can be done in a number of ways:
- 使用锁定文件(第一个函数锁定文件名"f.lok",第二个函数根据该评估检查锁定文件是否存在并且执行或不执行)
- 在数据库中设置一个标志(不推荐)
- 按照@JvdBerg的建议使用信号灯(最快)
编写并发应用程序时,请始终注意竞争状况和死锁!
When coding concurrent application always beware of race conditions and deadlocks!
更新 使用信号量(未经测试):
UPDATE using semaphores (not tested):
<?php
define('SEM_KEY', 1000);
function noconcurrency() {
$semRes = sem_get(SEM_KEY, 1, 0666, 0); // get the resource for the semaphore
if(sem_acquire($semRes)) { // try to acquire the semaphore. this function will block until the sem will be available
// do the work
sem_release($semRes); // release the semaphore so other process can use it
}
}
要使用sem_ *函数,必须在sysvsem支持下编译PHP
PHP needs to be compiled with sysvsem support in order to use sem_* functions
这是有关在PHP中使用信号灯的更深入的教程:
Here's a more in depth tutorial for using semaphores in PHP:
http://www.re-cycledair.com/php-dark-艺术信号量
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