sort files by date in PHP

This would get all files in path/to/files with an .swf extension into an array and then sort that array by the file's mtime

$files = glob('path/to/files/*.swf');
usort($files, function($a, $b) {
    return filemtime($b) - filemtime($a);
});

The above uses an Lambda function and requires PHP 5.3. Prior to 5.3, you would do

usort($files, create_function('$a,$b', 'return filemtime($b)-filemtime($a);'));

If you don't want to use an anonymous function, you can just as well define the callback as a regular function and pass the function name to usort instead.

With the resulting array, you would then iterate over the files like this:

foreach($files as $file){
    printf('<tr><td><input type="checkbox" name="box[]"></td>
            <td><a href="%1$s" target="_blank">%1$s</a></td>
            <td>%2$s</td></tr>', 
            $file, // or basename($file) for just the filename w\out path
            date('F d Y, H:i:s', filemtime($file)));
}

Note that because you already called filemtime when sorting the files, there is no additional cost when calling it again in the foreach loop due to the stat cache.

You need to put the files into an array in order to sort and find the last modified file.

$files = array();
if ($handle = opendir('.')) {
    while (false !== ($file = readdir($handle))) {
        if ($file != "." && $file != "..") {
           $files[filemtime($file)] = $file;
        }
    }
    closedir($handle);

    // sort
    ksort($files);
    // find the last modification
    $reallyLastModified = end($files);

    foreach($files as $file) {
        $lastModified = date('F d Y, H:i:s',filemtime($file));
        if(strlen($file)-strpos($file,".swf")== 4){
           if ($file == $reallyLastModified) {
             // do stuff for the real last modified file
           }
           echo "<tr><td><input type=\"checkbox\" name=\"box[]\"></td><td><a href=\"$file\" target=\"_blank\">$file</a></td><td>$lastModified</td></tr>";
        }
    }
}

Not tested, but that's how to do it.

An example that uses RecursiveDirectoryIterator class, it's a convenient way to iterate recursively over filesystem.

$output = array();
foreach( new RecursiveIteratorIterator( 
    new RecursiveDirectoryIterator( 'path', FilesystemIterator::SKIP_DOTS | FilesystemIterator::UNIX_PATHS ) ) as $value ) {      
        if ( $value->isFile() ) {
            $output[] = array( $value->getMTime(), $value->getRealPath() );
        }
}

usort ( $output, function( $a, $b ) {
    return $a[0] > $b[0];
});