Memcached::get()

(PECL memcached >= 0.1.0)

检索一个元素

说明

publicMemcached::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The $cas_token is no longer valid argument.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 :)