create_function()has been DEPRECATED as of PHP 7.2.0. Relying on this function is highly discouraged.
For the sake of posterity, in case the forum post linked in the accepted answer is lost or unclear to some, the relevant code needed is:
<?php $myarray = glob("*.*"); usort($myarray, create_function('$a,$b', 'return filemtime($a) - filemtime($b);')); ?>
Tested this on my system and verified it does sort by file mtime as desired. I used a similar approach (written in Python) for determining the last updated files on my website as well.