apc_store

brunohass2303 at gmail dot com (2013-06-05 18:10:14)

Functions to update arrays and get the values from an unique key.

<?php

function apc_array_store($apc_var, $key, $valor)
{
    $apcTemp = array();
    
    if ( $valor == NULL ) return FALSE;
    
    if ( $apcTemp = apc_fetch($apc_var) ) // Verifica se a variavel $apc_var existe no cache APC
    { // Se existir
        if ( !array_key_exists($apcTemp, $key) ) // Verifica se a chave $key existe no array 
            $apcTemp[$key] = $valor; // Se $valor n?o for NULL, adiciona no array
        
        if ( apc_store("$apc_var", $apcTemp) ) // Tenta atualizar o array no cache
             return TRUE;
        else return FALSE;
    }
    else
    { // Se a variavel $apc_var nao existir no cache adiciona
        if ( $valor == NULL ) // Se $valor for NULL retorna FALSE
            return FALSE;
        else 
        {    // Se $valor n?o for NULL, cria o array
            $apcTemp[$key] = $valor;
            
            if ( apc_add("$apc_var", $apcTemp) ) // Tenta adicionar o array no cache
                 return TRUE;
            else return FALSE;
        }
    }
    
}

function apc_array_fetch($apc_var, $key)
{

    if ( $apcTemp = apc_fetch($apc_var) ) // Verifica se a variavel $apc_var existe no cache APC
    { // Se existir
        if ( !array_key_exists($apcTemp, $key) ) // Verifica se a chave $key existe no array 
                return FALSE; // Se n?o existir retorna FALSE
            else
                return $apcTemp[$key]; // Se existir retorna o valor
    }
    else // Se n?o existir
        return FALSE;
    
}

?>

Anonymous (2013-05-31 09:44:20)

Interesting info to read before apc_store() implementation:
http://stackoverflow.com/questions/10494744/deadlock-with-apc-exists-apc-add-apc-php
http://stackoverflow.com/questions/4468805/apc-values-randomly-disappear/4532905#4532905

alexey dot maksutov at gmail dot com (2013-05-22 21:13:53)

APC does serialization/deserialization during store/fetch operations as well as it calls __sleep()/__wakeup(), or Serializable::serialize()/Serializable::unserialize(). Tested on PHP 5.4.1.0.

elfi47 (2012-10-20 19:04:27)

use apc_store() if you want to find out if the result of apc_delete(), apc_fetch(), apc_add(), ..... is REALLY FALSE or you have a problem with APC.

<?php
if (!apc_fetch('key')) {
   if (!apc_store('apc_check', 1, -1)) {
        // you have a problem with APC
   }
   else {
       // apc works but variable isn?t set
   }
}
?>

MaxTheDragon at home dot nl (2012-09-21 13:39:30)

When specifying a ttl (Time-To-Live), you are allowed to use negative values. This causes a stored entry to be invalidated immediately, but note that it will not physically be removed until you read (eg. apc_fetch or apc_exists) it:

<?php
apc_store('testKey', 'testValue', -1); // ... or any negative integer.

// at this point, the key exists physically but is already technically invalidated by the ttl.

$test = apc_fetch('testKey'); // $test equals false.

// at this point, the key no longer exists physically.
?>

Although you could mimic apc_delete with a negative TTL (like when dealing with cookies), note that the difference is that apc_delete actually physically removes the entry.

This example comes in handy when you want to unit-test a class that uses APC. It's faster to use a negative TTL than a positive in combination with a sleep call to test whether the cache entry has actually been deleted. Other than that I can't think of any situations in which you could use this example, but I'm simply pointing out that doing this will not generate Exceptions or errors.

danil dot gazizov at gmail dot com (2012-02-03 11:49:38)

Don't save empty arrays and empty values. Sometimes, you can get wrong apc_exists($someKey) result, that this key doesn't exists.

pere dot cil dot remove dot this at wanadoo dot fr (2011-12-09 01:49:41)

Note that caching resources is not possible; even if the apc cache doesn't seems to call the serialize / unserialize functions, that doesn't means that resources can be cached!

Small non-working example:

<?php
// Setter code
$r = fopen( '/tmp/test.txt', 'r' );
var_dump( $r );
apc_store( 'test', $r );
?>

<?php
// Getter code
$d = apc_fetch( 'test' );
var_dump( $d );
echo fread( $d, 1024 );
?>

var_dump( $d ) returns Resource #n of type (Unknown). The resource is still here, but unavailable.

Dominik Deobald / Interdose (2010-11-17 11:17:49)

It might be interesting to note that storing an object in the cache does not serialize the object, i.e. does not call the __sleep()/__wakeup() or serialize()/unserialize() methods.

TaRaKa (2010-08-25 01:32:34)

Note APC version 3.1.3 there is a bug (http://pecl.php.net/bugs/bug.php?id=16814) that will display a cache slam averted warning for all writes to a cache var that exists. Slam checking can be disabled by setting apc.slam_defense = 0.

eda-qa at disemia dot com (2010-01-05 07:40:48)

Note that the TTL only takes effect when you attempt to access the variable again (at least in my version). That is, just issuing a new request to a page won't clear outdated items -- you have to call apc_fetch on that specific item.
If you call apc_info after the TTL of an item it will still be listed.
This is important if you are expecting items to be cleared to conserve memory.

sebastian at 7val dot com (2008-03-10 00:53:32)

Note that since APC 3.0.15 or 3.0.16, the time-to-live-feature does not work within the same request (see http://pecl.php.net/bugs/bug.php?id=13331).

JaskaS (2007-03-01 06:06:23)

if you want to store array of objects in apc use ArrayObject wrapper (PHP5).

<?php
$objs = array();
$objs[] = new TestClass();
$objs[] = new TestClass();
$objs[] = new TestClass();

//Doesn't work
apc_store('objs',$objs,60);
$tmp = apc_fetch('objs'); 
print_r($tmp);

//Works
apc_store('objs',new ArrayObject($objs),60);
$tmp = apc_fetch('objs'); 
print_r($tmp->getArrayCopy());

?>

Roberto Spadim (2007-01-12 02:11:49)

be sure that setting FALSE values can be wrong returned from fetch since fetch return FALSE on errors

php at tequilasolutions dot com (2006-11-03 03:45:27)

Seems to be no (easy) way at the to know how old a value fetched is and to check whether it is out of date.

I've made these wrappers so that you can fetch and store values based on a udt returned from get_last_modified_date() which should return a udt of when your data was last changed, and hence needs junking out of the cache.

<?php
function apc_fetch_udt($key){
    $g = apc_fetch($key);
    if ($g){
        list($udt,$val) = $g;
        if (get_last_modified_date()<$udt) {
            $val = unserialize($val);
            return $val; 
        } else {
            apc_delete($key);
        }
    }
}
function apc_store_udt($key,$g){
    $udt = time();
    $g   = serialize($g);
    $apc = array($udt,$g);
    apc_store($key, $apc);
}
?>

Sudhee (2006-10-30 04:09:43)

It should be noted that apc_store appears to only store one level deep. So if you have an array of arrays, and you store it. When you pull it back out with apc_fetch it will only have the top level row of keys with nulls as the values of each key.

Solution to this, is to serialize the data before storing it in the cache and unserialize it while retrieving from the cache.