Date sorting for a server php script

I have a simple server script (one php file) which shows all the files on my ftp server in the form of links etc. in the browser. It sorts the files by descending alphabetic order by default and there does not seem to any setting variable in second preferences file to change it. So I wanted a change in this original php file to display the files in the descending order by date i.e. newest files at the top. I will send the two files and the programmer will work on one's own php server and make the small changes which are required for this sorting while keeping everything else the same.