Memcache::get

(PECL memcache >= 0.2.0)

Memcache::get — 从服务端检回一个元素

说明

string Memcache::get ( string $key [, int &$flags ] )

array Memcache::get ( array $keys [, array &$flags ] )

如果服务端之前有以key作为key存储的元素，Memcache::get()方法此时返回之前存储的值。

你可以给Memcache::get()方法传递一个数组（多个key）来获取一个数组的元素值，返回的数组仅仅包含从服务端查找到的key-value对。

参数

key: 要获取值的key或key数组。
flags: 如果给定这个参数（以引用方式传递），该参数会被写入一些key对应的信息。这些标记和Memcache::set()方法中的同名参数意义相同。用int值的低位保留了pecl/memcache的内部用法（比如：用来说明压缩和序列化状态）。（译注：最后一位表明是否序列化，倒数第二位表明是否经过压缩，比如：如果此值为1表示经过序列化，但未经过压缩，2表明压缩而未序列化，3表明压缩并且序列化，0表明未经过压缩和序列化，具体算法可查找linux文件权限算法相关资料）

返回值

返回key对应的存储元素的字符串值或者在失败或key未找到的时候返回FALSE。

范例

Example #1 Memcache::get() 示例


<?php

/* procedural API */
$memcache_obj = memcache_connect('memcache_host', 11211);
$var = memcache_get($memcache_obj, 'some_key');

/* OO API */
$memcache_obj = new Memcache;
$memcache_obj->connect('memcache_host', 11211);
$var = $memcache_obj->get('some_key');

/* 
你同样可以使用数组key作为参数，如果某个元素没有在服务端发现，结果数组中将不会包含这些key。
*/

/* procedural API */
$memcache_obj = memcache_connect('memcache_host', 11211);
$var = memcache_get($memcache_obj, Array('some_key', 'another_key'));

/* OO API */
$memcache_obj = new Memcache;
$memcache_obj->connect('memcache_host', 11211);
$var = $memcache_obj->get(Array('some_key', 'second_key'));

?>

PHP手册 - N: 从服务端检回一个元素

用户评论:

Michael Brenden (17-Feb-2011 10:46)

Beware, if there's a backslash present in the key name then the results are unpredictable and random. I was generating keys like this: $mc_key = get_called_class(). $_COOKIE['crumb']; This works fine when get_called_class() returns CLASSNAME. But then I began using namespaces, and get_class_class() of course returned NAMESPACE\CLASSNAME Well that backslash sends Memcache into quite the tizzy. No errors, mind you, just insanity.

janis at unrepublic dot com (22-Mar-2010 10:00)

For me it was the case that if such key doesn't exist, null is returned not false.

nate (14-Oct-2008 04:18)

Be aware that when using the multi-key version, Memcache::get returns bool false if no servers are configured for the pool (and possibly if other errors occur as well while attempting to fetch). Also, Memcache class throws annoying warnings on every get/set/delete-type calls if you have no servers added to the pool. The following snippet var_dump's bool false, not an empty array like you might expect. <?php $cache = new Memcache; // no $cache->addServer calls (for example, due to temporarily disabling use of cache) // use @ symbol to ignore warning var_dump( @$cache->get(array('one', 'two')) ); ?>

marko at nastja dot com (30-Jul-2008 01:07)

It looks like memcache take only first 256 characters. So if you want to cache some (large) queries do md5 or similar before caching.

jakub dot lopuszanski at nasza-klasa dot pl (07-Jul-2008 03:39)

If deserialization fails for some reason, that is when memcache server returned flag 1 set, but the value was not a correctly serialized PHP data, then Memcache::get acts in a following way: If it was called with a single key to retrieve, then a warning is raised, but since it was not actually a bug of a server, the warning says something confusing like "Memcached Server Error: null" and the function returns bool(false). If it was called by passing an array (even with a single element in it), then the warning is not raised and the resulting array contains a value bool(false). Since there are some buffer overrun bugs present in Memcached Server, which from time to time cause overwriting of [part of] data and therefore rendering it impossible to deserialize, make sure to check if the result of Memcache::get contains only string, or deserialized structure. If the result is bool,dobule or long, then something went wrong.