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It seems there are issues when using APC to cache database result sets as PDOStatements. Any attempts I have made always result in an exception being thrown with the message: 'You cannot serialize or unserialize PDOStatement instances'
Keep in mind to always prefix or suffix your cache key names with something specific to your site/app/setup, to avoid the risk of your apc cache entries being overwritten/deleted/modified by someone else on the same server.
Assume we have some code like this:
<?php apc_store('config', $cfg); ?>
Now assume someone else on the same server is also using 'config' as the key passed to an apc_store(), apc_delete() (etc.) call in some other piece of code on the whole server.
Since you're both working on the exact same cache entry, all sorts of wierd things can happen, but the problem is not in your code at all.
If you don't want any APC info visible without logging in, insert this code at line 173 of apc.php:
<?php
if (!$AUTHENTICATED) {
echo '<div class="authneeded">You need to login to see the user values here!<br/> <br/>';
put_login_link("Login now!");
echo '</div>';
die();
}
?>
In IIS6 you can't use php_apc.dll with application pools or webgardens (Multi-Instance/Multi-Threading). Maybe this applies even to all Multithreading environments - i don't know.
When you try it, the Application pools terminate when requests run simultaneously.
If you don't really need caching and plan to use it for one page only, you could try an alternative; writing a file and then flushing it back if specified time hasn't passed. I use it to read and parse third party websites, to check for new subtitles and output a RSS xml file.
<?php
if ((is_file($_SERVER['SCRIPT_FILENAME'].'.cached'))
&& (time()-filemtime($_SERVER['SCRIPT_FILENAME'].'.cached') < 3600))
{
readfile($_SERVER['SCRIPT_FILENAME'].'.cached');
exit;
}
// (the php script itself goes here)
echo $out;
$fp = fopen($_SERVER['SCRIPT_FILENAME'].'.cached', 'w');
fwrite($fp, $out);
fclose($fp);
?>
Note, that this only works for pages, which are without GET or POST variables, sessions, etc. You can change the number of seconds the cache works for (3600 = an hour). Also, use "$out.=" instead of "echo" command. Just store all output to that variable (if you need to use it inside a function, use "global $out" instead).
This workaround was written in about 5 minutes and may contain bugs.
In windows, if you load php_apc.dll but do not enable it, apache may crash when attempting to restart or stop.
So, if you've not enabled APC but are loading it, comment out the loading.
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