Clean Folder in PHP

$debug='false';
$folder='book/pages/';

if ($debug) {
// echo "Cleaning folder $folder ...
";
}

$d = dir($folder);

while (false !== ($entry = $d->read())) {

$isdir = is_dir($folder."/".$entry);

if (!$isdir and $entry!="." and $entry!="..") {

unlink($folder."/".$entry);

} elseif ($isdir and $entry!="." and $entry!="..") {

empty_folder($folder."/".$entry,$debug);

rmdir($folder."/".$entry);

}
}
$d->close();