Blogging since 2008 until 2010

A generic caching function for PHP

A short post is better than none. I threw together a generic caching function today; thought I'd share.

function createCached($fn$ttl = 100){
    return function() use($fn$ttl){
        $args = func_get_args();
        if (!is_string($fn)){
            //Use reflection to get a unique, reproducible 
            //identifier for an anonymous function
            $r = new ReflectionFunction($fn);
            $key = md5(
        } else {
            $key = md5($fn.serialize($args));
        $result = apc_fetch($key$success);
        if ($successreturn $result;
        $result = call_user_func_array($fn$args);
        return $result;

It's pretty simple and immature (read: no error checking) at the moment, but here's an example...

function helloWorld($name){
    echo "You will only see this when the result is not cached\\n";
    return "Hello, {$name}!\\n";

echo helloWorld('Tom');
$cachedHelloWorld = createCached('helloWorld'10);
echo $cachedHelloWorld('Tom');
echo $cachedHelloWorld('Tom');

The output of that is something a little like this:

You will only see this when the result is not cached
Hello, Tom!
You will only see this when the result is not cached
Hello, Tom!
Hello, Tom!

As you can (hopefully) see, the first call too helloWorld() just calls it directly. The call to createCached() creates a cached version of helloWorld() with a Time To Live of 10 seconds. The first call to the resultant anonymous function calls helloWorld() and caches the result using APC. The third and final call just returns the cached result.

You can pass in an anonymous function instead of the name of a function too:

$myFn = createCached(function(){
    $result_array = someIntensiveFunction();
    return $result_array;
}, 3600);


This would create a function that caches the sorted output of someIntensiveFunction() for an hour. Very handy if someIntensiveFunction() lives up to it's name.

If you've got a big code-base with a lot of fetcher functions this approach can be pretty handy; you can cache the output of your most used functions without cluttering them up with caching code.


There's a whole bunch wrong with my suggested code at the moment. I just wanted to get it out of my head while it's still fresh. It won't work with object methods and it's not very well tested, for example. I might get time in the next 6 months or so (that is my average interval between blog posts isn't it?) to write some tests for it and expand a little on the idea. Or I might just write an equivalent in JavaScript for comparison.

First posted: Tue, 15 Jun 2010 17:57:05 +0000