Is there a way to detect changes in a folder using php on both windows and linux?

Monitoring the filesystem for changes is a task that should be solved outside PHP. It's not really built to do stuff like this.

There are ready-made tools on both platforms that can monitor file changes that could call a PHP file to do the further processing.

For Linux:

• How to efficiently monitor a directory for changes on linux? (looks best at a quick glance)
• Monitor Directory for Changes

For Windows:

• How to monitor a folder for changes, and execute a command if it does, on Windows?
• The second answer in How can I monitor a Windows directory for changes?

So if you are checking compared to the last time you checked rather than just being updated as soon as it changes you could do the following.

You could create an MD5 of a directory, storew this MD5 then compare the new MD5 with the old to see if things have changed.

The function below taken from http://php.net/manual/en/function.md5-file.php would do this for you.

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));}

This is rather inefficient though, since as you probably know, there is no point checking the entire contents of a directory if the first bit is different.

I would

1. scan all folders/files and create an array of them,
2. save this somewhere
3. run this scan again later [to check if the array still looks the same].

As you have the entire data structure from "time 1" and "now", you can clearly see what has changed. To crawl through the directories, check this: http://www.evoluted.net/thinktank/web-development/php-directory-listing-script and this http://phpmaster.com/list-files-and-directories-with-php/