<?php
$files = glob('imagecache/*', GLOB_BRACE);
usort($files, 'filemtime_compare');

function filemtime_compare($a, $b)
{
    return filemtime($a) - filemtime($b);
}

$i = 0;
$show = 1000;

$today = mktime(date('h,i,s,m,d,Y'));
$onemonth = $today-47645;

foreach($files as $file)
{
    if($i == $show) break; else ++$i;
    $fileunixtime = filemtime($file);

    if ($fileunixtime <= $onemonth)    unlink($file);
}
?>