Memcache::set

(PECL memcache >= 0.2.0)

Memcache::setЗапись элемента

Описание

bool Memcache::set ( string $key , mixed $var [, int $flag [, int $expire ]] )

Memcache::set() записывает элемент со значением var на сервере memcache с указанным ключем key. Параметр expire задает время жизни элемента. Если он развен 0, то элемент никогда не устареет (но memcached сервер не гарантирует что элемент будет постоянно храниться в кеше и он может быть удален для освобождения места для новых элементов). Вы можете использовать константу MEMCACHE_COMPRESSED в качестве значения для параметра flag если вам требуется сжатие "на лету" (используется zlib).

Замечание:

Помните, что ресурсы (например дескрипторы файлов или подключений) не могут быть сохранены в кеше, потому что они не могут быть сериализованы.

Так же вы можете использовать функцию memcache_set().

Список параметров

key

Ключ, с которым будет ассоциировано значение элемента.

var

Переменная для сохранения. Строковые и числовые значения сохраняются как есть, а остальные типы сериализируются.

flag

Используйте MEMCACHE_COMPRESSED для сохранения элементов с использованием сжатия (используется zlib).

expire

Время жизни элемента. Если равно нулю, элемент никогда не устаревает. Так же вы можете использовать Unix timestamp или число секунд начиная с текущего момента, однако, число секунд не может быть больше 2592000 (30 дней).

Возвращаемые значения

Возвращает TRUE в случае успешного завершения или FALSE в случае возникновения ошибки.

Примеры

Пример #1 Пример использования Memcache::set()

<?php
/* процедурный стиль */

/* подключение к memcached серверу */
$memcache_obj memcache_connect('memcache_host'11211);

/*
установить значение элемента с ключем 'var_key'
используя 0 во flag, без использования сжатия со
временем жизни 30 секунд
*/
memcache_set($memcache_obj'var_key''some variable'030);

echo 
memcache_get($memcache_obj'var_key');

?>

Пример #2 Пример использования Memcache::set()

<?php
/* объектный стиль */

$memcache_obj = new Memcache;

/* подключение к memcached серверу */
$memcache_obj->connect('memcache_host'11211);

/*
установить значение элемента с ключем 'var_key' использую сжатие "на лету" и
временм жизни 50 секунд.
*/
$memcache_obj->set('var_key''some really big variable'MEMCACHE_COMPRESSED50);

echo 
$memcache_obj->get('var_key');

?>

Смотрите также

  • Memcache::add() - Добавляет элемент с указанным ключем
  • Memcache::replace() - Заменяет значение существующего элемента

add a note add a note

User Contributed Notes 9 notes

up
12
Sc00bz
10 years ago
This is just two minor things about memcache that might not be perfectly clear, the limits on key and data sizes and what happen to flags in the memcache protocol.

* There is a max key size of 250 anything bigger gets truncated. There is also a (1MB - 42 bytes) limit on the data.

* In the memcache protocol there is a 16bit, 32bit in newer version, flag that you can set to whatever you want because memcache doesn't do anything with the flags. The php api doesn't let you get the flags because php uses the flags for php's own use such as "MEMCACHE_COMPRESSED" and I decided to test if it was doing something because it wasn't part of the memcache protocol.

<?php
$memcache
= new Memcache();
$memcache->connect("127.0.0.1", 11211);

// Since memcache truncates the keys at 250 bytes both the get "250 a's" and "251 a's" will find the key in the cache
echo "*** Truncate key test ***<br>";
echo
"set 251: " . ($memcache->set(str_repeat("a", 251), "value", 0, 1) ? "t" : "f") . "<br>";

echo
"get 249: " . (($ret = $memcache->get(str_repeat("a", 249))) !== false ? "'$ret'" : "f") . "<br>";
echo
"get 250: " . (($ret = $memcache->get(str_repeat("a", 250))) !== false ? "'$ret'" : "f") . "<br>";
echo
"get 251: " . (($ret = $memcache->get(str_repeat("a", 251))) !== false ? "'$ret'" : "f") . "<br>";
echo
"delete: " . ($memcache->delete(str_repeat("a", 250)) ? "t" : "f") . "<br><br>";

echo
"*** Compress value test ***<br>";
echo
"set 1024*1024-42: " . ($memcache->set("test", str_repeat("a", 1024*1024-42), 0, 1) ? "t" : "f") . "<br>";
echo
"set 1024*1024-41: " . ($memcache->set("test", str_repeat("a", 1024*1024-41), 0, 1) ? "t" : "f") . "<br>";
echo
"set 1024*1024 compressed: " . ($memcache->set("test", str_repeat("a", 1024*1024), MEMCACHE_COMPRESSED, 1) ? "t" : "f") . "<br>";
echo
"delete: " . ($memcache->delete("test") ? "t" : "f") . "<br>";
$memcache->close();
?>

Output:
*** Truncate key test ***
set 251: t
get 249: f
get 250: 'value'
get 251: 'value'
delete: t

*** Compress value test ***
set 1024*1024-42: t
set 1024*1024-41: f
set 1024*1024 compressed: t
delete: t
up
7
wbonde at yakabod dot com
6 years ago
The max time for expiration (without having to worry about deletions when necessary as with 0 seconds) is 2,592,000 seconds (30 days).

Specifying an expiration value above that will return false, but will NOT throw in error so it is easy to miss.
up
6
argyleblanket
9 years ago
Using set more than once for the same key seems to have unexpected results - it does not behave as a "replace," but instead seems to "set" more than one value for the same key.  "get" may return any of the values.

This was tested on a multiple-server setup - behaviour may be different if you only have one server.

Remedy is to use a combination of replace and set:

<?php
$result
= $memcache->replace( $key, $var );
if(
$result == false )
{
   
$result = $memcache->set( $key, $var );
}
?>
up
2
duerra at nospam dot yahoo dot com
7 years ago
If you're interested in using compression, please note that, at least for PHP version 5.3.2 and Memcache version 3.0.4, when retrieving a key who's value is a numeric or boolean type, PHP throws a notice of the following:

Message: MemcachePool::get(): Failed to uncompress data

The way around this is to test your variable type before setting or adding it to Memcache, or even cast it as a string. 

<?php
$key
= 'mc_key';
$value = 12345;
$compress = is_bool($value) || is_int($value) || is_float($value) ? false : MEMCACHE_COMPRESSED;

$mc= new Memcache;
$mc->connect('localhost', 11211);
$mc->set($key, $value, $compress);

echo
$mc->get($key);

//Alternative is to cast the variable
$value = is_scalar($value) ? (string)$value : $value;
$mc->set($key, $value, MEMCACHE_COMPRESSED);
?>
up
1
Stephen from veedow.com
9 years ago
I ran into problems using the MEMCACHE_COMPRESSED flag when storing small amounts of data, such as an integers.

For expample.

<?php
Memcache
::set('integer', 123456, MEMCACHE_COMPRESSED);
//would return true

Memcache::get('integer');
//would return false
?>

This problem went away when I removed the MEMCACHE_COMPRESSED flag for values that were small.
up
0
jcastromail at yahoo dot es
3 months ago
If you get the next message

"The lowest two bytes of the flags array is reserved for pecl/memcache internal use"

Then try the next operations:
a) try to use Memcached instead of Memcache.
b) switch the compressed value
  $memcache->set($key,$value,MEMCACHE_COMPRESSED)
  or
  $memcache->set($key,$value,0)
up
-1
effeesse gmail com
7 years ago
if you want to cache an image created on-the-fly you can do:

<?php
ob_start
();
imagepng($image);
$memcache->set("my_image", ob_get_contents(), false, $cache_time);
ob_end_clean();
?>

then you could access the chached image as simple variable:
<?php $my_image = $memcache->get("my_image"); ?>

so, in short, you have to buffer the output
up
-5
aamthor at advertzoom dot de
5 years ago
to put some things right:

max expiration time: RTFM, it's written here.

max amount of data: almost unlimited as long as your server can bear it.

speed and pace:
well, thats another thing. We had a couple of data records which for application reasons must be kept in memory. Since the bunch of data is big and doesn't change very often, we considered caching it to memcache instead of retrieving it from the DB each and every time.

This isn't a general advice nor any quality statement, but we did a couple of tests with serialized arrays (50 MB), compressed and uncompressed and it turned out that in our particular scenario, memcache is much slower than the DB (mySql).

In general, one can not predict on the behavior of memcache in certain scenarios but always need to make some testing and benchmarking upfront before starting to deploy things to a live system.

Despite of the tests above, we are still using memcache for session caching instead of file system, since there are certain other things to consider and the amount of data is always small (few KB)
up
-13
jakub dot lopuszanski at nasza-klasa dot pl
9 years ago
The lowest byte of the int is reserved for pecl/memcache internal usage (e.g. to indicate compression and serialization status).
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