shardFilename.inc

/* Use as standalone function or static method of any object.
 * Set default $shardLevel to a value relevant for your usercase (e.g. +3 for MD5 filenames, -2 for ID filenames, etc.)
 */
 
  /**
	 * Creates subfolders for storing files to prevent folder overloading by too many files.
	 *
	 * @param  mixed $filename (required) Basic filename without extension. Can be anything convertable to string valid for filenaming.
	 * @param  string $root (optional, default: '/') Where to start creating the subfolders. Set false to skip folder creation.
	 * @param  string $ext (optional, default: none) Extension for the file.
	 * @param  number $shardLevel (optional, default: -3) Maximum number of subfolders to create.
	 * 					For positive numbers will use letters from the beginning of the $filename, for negative numbers will use letters from the end of the $filename.
	 * 					Zero disables sharding and will only ensure $root folder exists and will create filepath from $root, $filename and $ext.
	 * 					Use PHP_INT_MAX or -PHP_INT_MAX for unlimited number of folders. Recommended maximum is 64 or less (based on OS limits).
	 * @return array
	 * 				shards Created subfolders in $root from member id (e.g. '5/4/3/' for ID 12345).
	 * 				filename Filename with extension from member id
	 * 				filepath Path of shards and filename
	 * 				rootpath Full path including root
	 * 				root Content of $root (so you don't need to keep it separately)
	 * @throws Exception When filename is empty.
	 */
	function shardFilename($filename, $root = '/', $ext = '', $shardLevel = 3) {
		$filename = '' . $filename; //convert to string
		if (empty($filename)) {
			throw new Exception('Missing filename for sharding.');
		}
		$len = strlen($filename);
		$path = '';
		for ($i = 0; $i < abs($shardLevel); ++$i) {
			if (($len - $i) < 2) { //do not shard for last letter
				break;        //e.g. 3/2/123.tmp for short name but 5/4/3/12345.tmp for longer
			}

			$path .= $filename[$shardLevel > 0 ? $i : $len - $i - 1] . '/';
		}

		if (false !== $root && !is_dir($root . $path)) {
			$umask = umask(0); //allow to create folder with all rights
			mkdir($root . $path, 0777, true);
			umask($umask); //return previous limits
		}

		return array(
			'root' => $root,
			'shards' => $path,
			'filename' => $filename . $ext,
			'rootpath' => $root . $path . $filename . $ext,
			'filepath' => $path . $filename . $ext,
		);
	}
	
	/* EXAMPLE:
	file_put_contents(shardFilename('12345', UPLOAD_PATH, '.tmp', 3)['rootpath'], $data); //will save to '/upload/1/2/3/12345.tmp'
	*/