Memcached
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Memcached::cas

(PECL memcached >= 0.1.0)

Memcached::casCompare and swap an item

说明

public bool Memcached::cas ( double $cas_token , string $key , mixed $value [, int $expiration ] )

Memcached::cas() performs a "check and set" operation, so that the item will be stored only if no other client has updated it since it was last fetched by this client. The check is done via the cas_token parameter which is a unique 64-bit value assigned to the existing item by memcache. See the documentation for Memcached::get* methods for how to obtain this token. Note that the token is represented as a double due to the limitations of PHP's integer space.

参数

cas_token

Unique value associated with the existing item. Generated by memcache.

key

The key under which to store the value.

value

The value to store.

expiration

The expiration time, defaults to 0. See Expiration Times for more info.

返回值

如果成功则返回 TRUE,失败则返回 FALSE。 The Memcached::getResultCode will return Memcached::RES_DATA_EXISTS if the item you are trying to store has been modified since you last fetched it.

范例

Example #1 Memcached::cas() example

<?php
$m 
= new Memcached();
$m->addServer('localhost'11211);

do {
    
/* fetch IP list and its token */
    
$ips $m->get('ip_block'null$cas);
    
/* if list doesn't exist yet, create it and do
       an atomic add which will fail if someone else already added it */
    
if ($m->getResultCode() == Memcached::RES_NOTFOUND) {
        
$ips = array($_SERVER['REMOTE_ADDR']);
        
$m->add('ip_block'$ips);
    
/* otherwise, add IP to the list and store via compare-and-swap
       with the token, which will fail if someone else updated the list */
    
} else { 
        
$ips[] = $_SERVER['REMOTE_ADDR'];
        
$m->cas($cas'ip_block'$ips);
    }   
} while (
$m->getResultCode() != Memcached::RES_SUCCESS);

?>

参见


Memcached
php 手册 | 脚本学堂 | 脚本编程 | 网站编程 | 系统管理 | 服务器配置 | 数据库管理 | Php教程 | python教程 | 正则表达式 | 批处理脚本 | Centos教程 | Linux基础教程