Memcached::get

(PECL memcached >= 0.1.0)

Memcached::get — 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

User Contributed Notes

letynsoft at gmail dot com 23-May-2017 10:58


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The $cas_token is no longer valid argument.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;

}

?>

denis_truffaut[A-T]hotmail[D-O-T]com 17-Jan-2011 06:01


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 :)

miha at hribar dot info 17-Jul-2009 01:31


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 :)