(PECL apc >= 3.0.0)
apc_store — Cache a variable in the data store
Cache a variable in the data store.
Note: Unlike many other mechanisms in PHP, variables stored using apc_store() will persist between requests (until the value is removed from the cache).
key
Store the variable using this name. keys are
cache-unique, so storing a second value with the same
key will overwrite the original value.
varThe variable to store
ttl
Time To Live; store var in the cache for
ttl seconds. After the
ttl has passed, the stored variable will be
expunged from the cache (on the next request). If no ttl
is supplied (or if the ttl is
0), the value will persist until it is removed from
the cache manually, or otherwise fails to exist in the cache (clear,
restart, etc.).
valuesNames in key, variables in value.
Returns TRUE on success or FALSE on failure.
Second syntax returns array with error keys.
Example #1 A apc_store() example
<?php
$bar = 'BAR';
apc_store('foo', $bar);
var_dump(apc_fetch('foo'));
?>
The above example will output:
string(3) "BAR"
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());
?>
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.
"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."
This is not a bug. Surprisingly, it has been assigned a bug id.It is obviously not a bug, because there is a man-made error message, as well as a switch to turn off slam checking.
Think about it, would you release code which modifies core system files without warning? No, you would make a warning for the user. Same is true with shared memory.
I happen to think it is a good feature, it tells you are overwriting something... And if you dislike it, turn it off using that setting, or use an @ in front of the function calls...
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.
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( $d ) returns Resource #n of type (Unknown). The resource is still here, but unavailable.
Note that since APC 3.0.15 or 3.0.16, the time-to-live-feature does not work within the same request (see http://pecl.php.net/bugs/bug.php?id=13331).
Don't save empty arrays and empty values. Sometimes, you can get wrong apc_exists($someKey) result, that this key doesn't exists.
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.
be sure that setting FALSE values can be wrong returned from fetch since fetch return FALSE on errors
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 $valor não for NULL, adiciona no array
if ( apc_store("$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 não 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 não existir retorna FALSE
else
return $apcTemp[$key]; // Se existir retorna o valor
}
else // Se não existir
return FALSE;
}
?>
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);
}
?>
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
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.
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.
