getting an image of a random file

<?php
$filedir = '/home/me/public_html/domain/swf/'; 
$newfile = '/home/me/public_html/domain/swffolder/something.swf'; 
$imgdir = '/home/me/public_html/domain/swf/';
$newimg = '/home/me/public_html/domain/imgfolder/something.swf'; 
function getRandomFile($start_dir)
        {
        /*
        returns the name of one random file from within a directory
        */
        
        chdir($start_dir);
        $dir = opendir('.');
        while (($myfile = readdir($dir)) !==false)
                {
                if ($myfile != '.' && $myfile != '..' && is_file($myfile) && $myfile != 'resource.frk')
                        {
                        $files[] = $myfile;
                        }
                }
        closedir($dir);
        chdir('../');
        srand ((float) microtime() * 10000000);
        $file = array_rand($files);
        return $files[$file];
        }
		
$filesize = 80000000;
while ($filesize > 400000) { //change this for file size

	$file = getRandomFile($filedir);
	$randfile = $filedir . $file ;
	$filesize = filesize($randfile);
	echo $randfile . ': ' . $filesize . ' bytes' . '<br>';
	
}
	
if (!copy($randfile, $newfile)) {
   echo "failed to copy $file...\n";
}

// outputs e.g.  somefile.txt: 1024 bytes
echo 'FINAL:' . $randfile . ': ' . $filesize . ' bytes';
?> 

PHP:

i added the $imgdir and $newimg lines.
what this script does is,it copys a random swf file out of the swf folder and puts it in the swffolder.also renaming it.
i also like it to grab the image file,which is named the same,but may be PNG or JPG and do the same like the swf file.