PHP cached json from multiple files

videolist.php

<?php

	/**
	 * Serves a JSON array with the contents of multiple JSON files.
	 * 
	 * Scans a $path for $target JSON files in nested folders, 
	 * collects the contents of each of those files and outputs 
	 * them as a JSON array. 
	 * ($path/{*dir}/$target)
	 * 
	 * The result is stored in a cache file along with the md5
	 * hash of the directory.
	 * 
	 * If the contents of $path have not changed (based on the md5), 
	 * the cached results are returned instead of scanning 
	 * the filesystem again.
	 * 
	 * @author Jovica Aleksic
	 */

	// User-defined variables
	//=====================================================
	// The path to the videos
	$path = "files/uploads/videos/";
	// The name of the target files that should be collected ($path/*/$target)
	$target = "description.json";

	// caching setup
	//=====================================================
	$cachedir = $_SERVER["DOCUMENT_ROOT"] . "/cache/videolist/";
	is_dir($cachedir) || mkdir($cachedir, 0700, true);
	$cachefile		= $cachedir . "cache.json";
	$md5_cachefile		= $cachedir . "cache.md5";
	$md5_now		= MD5_DIR($path);
	$md5_old		= file_exists($md5_cachefile) ? file_get_contents($md5_cachefile) : "";
	
	
	// serve the results
	//=====================================================
	header('Content-Type: application/json');
	if ($md5_now === $md5_old) {
		echo file_get_contents($cachefile);
	}
	else {
		$result = fetch_json($path, $target);
		file_put_contents($cachefile, $result);
		file_put_contents($md5_cachefile, $md5_now);
		echo $result;
	}
	die;

	
	// HELPER FUNCTIONS
	//=====================================================
	
	/**
	 * Collects multiple JSON files from a path and combines them to a JSON-encoded array.
	 * @param String $path The path to the directory that contains sub-directories with JSON files.  
	 * @param String $file The name of the JSON file that should be loaded from each sub-directory
	 * @return String An JSON-encoded array containing the contents of all found JSON files
	 */
	function fetch_json($path, $file) {
		$list = array();
		foreach (scandir($path) as $dir)
		{
			if (!is_dir("$path/$dir") || $dir == "." || $dir == "..") continue;
			$list[] = json_decode( file_get_contents("$path/$dir/$file") );
		}
		return json_encode($list);
	}
	
	/**
	 * Creates the md5 hash of an entire directory.
	 * http://php.net/manual/en/function.md5-file.php#75393
	 * @param String $dir The path to the directory to be indexed
	 * @return String The md5 hash of the directory
	 */
	function MD5_DIR($dir)
	{
	    if (!is_dir($dir))
	    {
	        return false;
	    }
	    
	    $filemd5s = array();
	    $d = dir($dir);
	
	    while (false !== ($entry = $d->read()))
	    {
	        if ($entry != '.' && $entry != '..')
	        {
	             if (is_dir($dir.'/'.$entry))
	             {
	                 $filemd5s[] = MD5_DIR($dir.'/'.$entry);
	             }
	             else
	             {
	                 $filemd5s[] = md5_file($dir.'/'.$entry);
	             }
	         }
	    }
	    $d->close();
	    return md5(implode('', $filemd5s));
	}