PHP: Best way to scan folders and process files

Searching the internet there seems to be many ways of traversing directories and files

Can some one suggest what the best way to this?

Within the "root" directory there should only be sub directories the name of each is required and processed separately
within each sub directory should only be files each one needs processing according to file extension

This is a windows system so how do I deal with'.' and '..'?

This is how far I've got and isn't tested more to give you an idea of what I'm trying to do

<?PHP
error_reporting(E_ALL);

$DS = DIRECTORY_SEPARATOR;

$root ="path" . $DS . "to" . $DS . "root";

$Dirs= scandir($root);
foreach($Dirs as $dir){

//$dir name is wanted 
$dh  = opendir($dir);
while (false !== ($fileName = readdir($dh))) {
    $ext = substr($fileName, strrpos($fileName, '.') + 1);
    if($ext == "html"){
       $htmlFile = $dir . $DS . $fileName;
       // Open and Do stuff with html file
    }
    elseif(in_array($ext, array("jpg","jpeg","png"))){
        //Do other stuff
    }
    else{
     // Error code file type not needed
    }
 }
}