File Hash to multiple Subdirectoris

file_dir_hash.php

<?php
// https://stackoverflow.com/questions/23787785/how-to-use-hash-function-for-storing-4-million-images-in-file-system

// $id = A unique identifier (a filename)
//       It could be useful to make this id the same for the original, 
//       as well as any thumbnails. Your image and variants will all
//       then end up in the same directory.

// $levels_deep = The number of directories deep you want to go.
//                Want more levels? Use a hashing method with a longer
//                output, such as sha1 (40 characters).

function _getDir($id, $levels_deep = 32) {
    $file_hash   = md5($id);
    $dirname     = implode("/", str_split(
        substr($file_hash, 0, $levels_deep)
    ));
    return $dirname;
}



function _store($dirname, $filename) {
    // The `true` flag here will have `mkdir` create directories recursively.  
    if(!file_exists($dirname) && !mkdir($dirname, 0777, true))
        throw new Exception("Could not create directory " . $dirname);

    return file_put_contents(
        $dirname . "/" . $filename,
        "Contents of example file.\n"
    );
}



// Example
store(getDir("myfile.jpg", 4), "myfile.jpg");

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