apc_exist() does not exist? - php

Question

I'm having some hard time getting PHP APC to work. Here's my test code:
<form>
<input type="text" name="apc">
<input type="submit">
</form>
<?php
apc_store('foo','FOO');
if (isset($_GET['apc'])) {
apc_store($_GET['apc'],$_GET['apc']);
}
?>
<pre>CACHE INFO (USER): <?php print_r(apc_cache_info("user",false)); ?></pre>
<pre>CACHE INFO: <?php print_r(apc_cache_info()); ?></pre>
<pre>FOO: <?php print_r(apc_fetch("foo")); ?></pre>
<pre>BAR: <?php print_r(apc_fetch("bar")); ?></pre>
<pre><?php if (apc_exists("bar")) { ?>bar exists!<?php } else { ?>bar does not exist!<?php } ?></pre>
<?php apc_clear_cache(); ?>
In short: you fill the form and the inserted value gets stored in APC. The key "foo" is always stored. You can try storing "bar" to see apc_fetch() working with a newly added key.
What works OK:
apc_store()
apc_fetch()
What does not:
apc_cache_info() (regardless of which parametres I pass to the function) always prints an empty array, despite apc_fetch() retrieving data successfully
apc_clear_cache() never clears the cache ("bar" is always displayed once input). This is true both if I provide a "user" parametre or leave the function with no parametres.
calling apc_exists() yields a fatal error: call to undefined function apc_exists()
In case it's helpful: I'm running Zend Server CE 5.6.0 (fresh install, finished half an hour ago), with PHP 5.3.9. Same happened with a more antique version of Zend Server CE yesterday (running PHP 5.3.5). I do not know which version of APC ships with Zend Server, phpinfo() only shows APC is enabled. I am on a Windows machine (Windows 7 Professional, 32 bit).
So. What's wrong here? Issues with my code? Maybe Zend Server ships with an older version of APC that just is buggy and/or does not support the functions I'm trying to use? Any clues?
[EDIT]
Inspired by clues provided by #Hannes, I modified the code, adding:
<?php
if (!function_exists('apc_exists') {
function apc_exists($key) { return (boolean)apc_fetch($key); }
}
?>
Since no error is raised, the code passes to the next line and the cache is cleared OK. This must have been why it wasn't cleared in the first place.
Still, apc_cache_info() doesn't return anything...

Answer 1

apc_exists is available for PECL apc >= 3.1.4 http://www.php.net/manual/en/function.apc-exists.php so your APC Version is probbaly lower, but its basically just a boolean wraper anyhow, a simple function shoud basically do the same:
function user_apc_exists($key){ return (bool) apc_fetch($key); }
in both cases your didint provide information for which cache to use, your probaby want user:
apc_clear_cache('user');
apc_cache_info('user);
http://www.php.net/manual/en/function.apc-clear-cache.php
http://www.php.net/manual/en/function.apc-cache-info.php

Answer 2

I ran across the same problem and after some debugging found out that the function in Hannes' answer works unless the stored data is a boolean false or an empty array.
This works also in those cases:
if (!function_exists('apc_exists')) {
function apc_exists($key) {
$success = false;
apc_fetch($key, $success);
return $success;
}
}