PHP Minimal Filesystem Function Cache

cacheFunctionCalls.php

<?php
// PHP Minimal Filesystem Function Cache
// by Greg Schoppe (http://gschoppe.com)
// copyright 2015 Greg Schoppe, GPL, BSD, and MIT licensed
// takes a function name as a string, and an array of the arguments to be passed to that function
// caches and returns the results of that function call (or the cached copy, if less than $TTL seconds old)
// Useful for rate-limiting cURL requests, or other high resource or rate limited functions
// WARNING:  DO NOT USE WITH ANONYMOUS FUNCTIONS (AKA: CLOSURES), ANY FUNCTION THAT PRODUCES SIDE EFFECTS,
//           OR WITH ANY FUNCTION THAT DOES NOT RETURN A SERIALIZABLE VALUE
function callFunctionWithCache($functionName, $arguments = array(), $TTL=3600, $purgeCache=false) {
    $cacheFolder  = "cache/";
    $manageCache  = true; // set to false if you intend to manage the cache folder with a cron job
    $cacheFileCap = 1000; // max number of files to cache
    $cacheMaxSize = pow(1024, 2)*32; // max total size of cache files in bytes (e.g. pow(1024, 2)*32 = 32Mb)
    $hysteresis   = .8; // when cache is cleaned, it will be culled back to this percent of the max, to prevent cache management from ocurring every time the script is run
    
    $cacheFile    = $TTL."-".$cacheFolder.md5(serialize($functionName))."-".md5(serialize($arguments)).".cache";
    // check cache
    if(file_exists($cacheFile) && ((time()-filemtime($cacheFile)) < $TTL)) {
        // get cached copy
        $response = json_decode(file_get_contents($cacheFile));
    } else {
        // do function call
        $response = call_user_func_array($functionName, $arguments);
        // store to cache
        $cache = json_encode($response);
        // only store if string is smaller than max cache size
        if(mb_strlen($cache, '8bit') < $cacheMaxSize) {
            file_put_contents($cacheFile, json_encode($response));
        }
        // clean up cache
        if($manageCache) {
            $filecount = 0;
            $files = glob($cacheFolder . "*.cache");
            if ($files) $filecount = count($files);
            $cacheSize = array_reduce($files, function($a, $b) {
                return($a + filesize($b));
            }, 0);
            
            if( ($filecount > $cacheFileCap) || ($cacheSize > $cacheMaxSize) ) {
                $cullCount = $filecount-($cacheFileCap*$hysteresis);
                $cullSize  = $cacheSize-($cacheMaxSize*$hysteresis);
                usort($files, function($a, $b) {
                    return filemtime($a) < filemtime($b);
                });
                $doCull = true;
                foreach($files as $file) {
                    if($cullCount<=0 && $cullSize <=0)
                        $doCull = false;
                    $fileParts     = explode('/', $file);
                    $fileName      = array_pop($fileParts);
                    $fileNameParts = explode('-', $fileName);
                    $fileTTL       = intval(array_pop($fileNameParts));
                    if((time()-filemtime($file)) > $fileTTL || $doCull) {
                        $filesize = filesize($file);
                        if(is_file($file))
                            unlink($file);
                        $cullSize -= $filesize;
                        $cullCount--;
                    }
                }
            }
        }
    }
    // empty cache if requested
    if($purgeCache) {
        $files = glob($cacheFolder . "*.cache");
        if ($files) {
            foreach($files as $file) {
                if(is_file($file))
                    unlink($file);
            }
        }
    }
    // return content
    return $response;
}