apc_fetch()

(PECL apc >= 3.0.0)

从缓存中取出存储的变量

说明

apc_fetch(mixed $key[,bool &$success]): mixed

从缓存中取出存储的变量

参数

$key

$key是使用apc_store()存储的键名。如果传递的是一个数组，则数组中的每个元素的值都被返回

$success

成功时为TRUE失败时FALSE。

返回值

存储一个变量或者一个数组失败时返回;FALSE

范例

Example #1 apc_fetch()范例

<?php
$bar = 'BAR';
apc_store('foo', $bar);
var_dump(apc_fetch('foo'));
?>

以上例程会输出：

string(3) "BAR"

更新日志

参见

• apc_store()Cache a variable in the data store
• apc_delete()从用户缓存中删除某个变量
• APCIterator

Note that the APC cache accessible from PHP running through Apache is not accessible from CLI-PHP (the commandline PHP version). They are 2 different APC caches.
If you are trying for example to run a script from cron that needs to access the same APC cache as your scripts (executed through Apache) with PHP CLI, use file_get_contents to execute the real script or to send over the data.
Doing so executes the script on Apache.
You can also specify a return value in order to move data around.
<?PHP
file_get_contents('http://localhost/actual_processing_script.php'); 
?>

Make sure to check the return value using a strict comparison if you want to know whether apc_fetch failed unless you want anything stored that can be evaluated to false to report an error aswell.
E.g. the following is bad:
<?php
  $result = apc_fetch("key");
  if(!$result) {
    //handle error
  }
?>
If key is an empty array or the value 0, it will naturally evaluate to false and trigger the error. To avoid this, do instead:
<?php
  $result = apc_fetch("key");
  if($result === false) {
    //handle error
  }
?>
Side note: avoid storing booleans in APC :)

hint for your fail over:
"return FALSE on failure" means NOT, it returns FALSE on APC-error.
it return FALSE if
- key doesnt exists
- value === FALSE
- APC error
even with $success you cant determine if its a APC-error. this is only for key exists / key doesnt exists things.

This function is often cited related to file upload tracking with PHP 5.2. So I thought this is a good place to put a warning.
If you setup PHP with FastCGI, you'll probably run into trouble using this function to get any information about a running upload. At least in my case, every HTTP request is handled by a different PHP process. I could track it with the getmypid() function, which returned a different value upon every request, but only from a limited set. Also, apc_cache_info() gave me all upload_* entries that were created in that process. So when the upload was initially catched by one PHP process, all progress updates must be fetched from the same process, too, because APC cache information does not seem to be shared across multiple processes handling that domain/virtual host. But that's impossible to tell because PHP has its own load management and serves every request by an arbitrary process.
So in short: When using FastCGI and multiple PHP processes (recommended for performance reasons), you cannot use APC upload tracking. You'll only get a status update every few requests.

Note apc_fetch() will return a copy of whatever is stored in the memory and not a reference to it.
For example:
<?php 
  
  class foo{
    public $bar;  
  }
  apc_add("foo", new foo());
  
  $fooGot  =  apc_fetch("foo");
  $fooGot->bar = 1234;  
  
  print_r(apc_fetch("foo"));  
?>
will print
foo Object ( [bar] => )

Another reason you might be getting null back from apc_fetch when using apc.rfc1867 is if you have only turned this option on using php_admin_value for a virtual host. It needs to be turned on globally in php.ini to work.

Anyone who has enabled apc.rfc1867 for a file upload progress bar. Please note that if you are not getting any results back or a Null() data set. Then set apc.rfc1867_freq to 10k or 100k or whatever you see fit like this.
apc.rfc1867_freq = 10k
In your php.ini.
Hope this helps some of you who were getting blank data results. It seems the 0 default setting will not work on some machines. Hope this helps!

Just to clarify the multi-get capability, the result is returned as an array with cache keys as the array keys. Any missing values re not returned, for example:
<?php
apc_delete('test1');
apc_delete('test2');
apc_add('test1', 'test1');
$cached = apc_fetch(array('test1', 'test2'));
var_dump($cached);
?>
gives
array(1) {
 ["test1"]=>
 string(5) "test1"
}
If no keys are found, you get an empty array.

As of version 3.0.13 APC (released 2007-02-24) you can perform multiple key fetches with apc_fetch. Very useful to further optimize your application! 
APC changelog:
http://pecl.php.net/package-changelog.php?package=APC
example:
<?php
apc_store('key1', 'value1');
apc_store('key2', 'value2');
$keys = array('key1','key2');
$result = apc_fetch($keys); //fetch multiple keys at once!
var_dump($result);
?>

I dont know is it a bug or feature but...
After apc_fetch and/or apc_store arrays loose their cursor
<?php
$array = array('foo',2,3,4,5);
var_dump(current($array)); //foo
apc_store('foo',$array);
$array2 = apc_fetch('foo');
var_dump(current($array2)); //false
?>