Memcached::get()
(PECL memcached >= 0.1.0)
检索一个元素
说明
public Memcached::get(string $key[,callback$cache_cb[,float &$cas_token]]): mixed
Memcached::get()返回之前存储在$key下的元素。如果元素被找到,并且提供了$cas_token参数,这个参数(译注:这个参数在函数定义中是引用参数,用来传出元素的版本标记,原理可以查阅乐观锁资料)将会包含该元素的CAS标记值。关于CAS标记值的使用,请查看Memcached::cas()的说明。另外,可以通过$cache_cb参数设置Read-through caching callback。
参数
- $key
要检索的元素的key。
- $cache_cb
通读缓存回掉函数或
NULL
.- $cas_token
检索的元素的CAS标记值。
返回值
返回存储在服务端的元素的值或者在其他情况下返回FALSE
。如果key不存在,Memcached::getResultCode()返回Memcached::RES_NOTFOUND
。
范例
Example #1 Memcached::get()示例#1
<?php $m = new Memcached(); $m->addServer('localhost', 11211); $m->set('foo', 100); var_dump($m->get('foo')); ?>
以上例程会输出:
int(100)
Example #2 Memcached::get()示例#2
<?php $m = new Memcached(); $m->addServer('localhost', 11211); if (!($ip = $m->get('ip_block'))) { if ($m->getResultCode() == Memcached::RES_NOTFOUND) { $ip = array(); $m->set('ip_block', $ip); } else { /* log error */ /* ... */ } } ?>
参见
- Memcached::getByKey() 从特定的服务器检索元素
- Memcached::getMulti() 检索多个元素
- Memcached::getDelayed() 请求多个元素
As of some version of php7 (i was not able to determine which exactly). The $cas_token is no longer valid argument. It has been removed in favor of flags argument, as it appears to be causing issues when subclassing the Memcached class. See https://github.com/php-memcached-dev/php-memcached/pull/214 for more details. Basically you need to <?php function memcacheGet($key, $cb = null, &$cas = null) { $m = memcacheGetObject(); if(empty($m)) return false; if(defined('Memcached::GET_EXTENDED')) { //Incompatible change in php7, took me 2 hours to figure this out, grrr $_o = $m->get($key, $cb, Memcached::GET_EXTENDED); $o = $_o['value']; $cas = $_o['cas']; } else { $o = $m->get($key, $cb, $cas); } return $o; } ?>
This method also returns false in case you set the value to false, so in order to have a proper fault mechanism in place you need to check the result code to be certain that a key really does not exist in memcached. <?php $Memcached = new Memcached(); $Memcached->addServer('localhost', 11211); $Memcached->set('key', false); var_dump($Memcached->get('key')); // boolean false var_dump($Memcached->getResultCode()); // int 0 which is Memcached::RES_SUCCESS ?> Or just make sure the values are not false :)
Note that this function can return NULL as FALSE, so don't make checks with === FALSE as with the old Memcache class, because it won't work. :O Use the not (!) operator and check the result code with getResultCode() as mentioned in the documentation :)