PHP read sub-directories and loop through files how to?

You need to add the path to your recursive call.

function readDirs($path){
  $dirHandle = opendir($path);
  while($item = readdir($dirHandle)) {
    $newPath = $path."/".$item;
    if(is_dir($newPath) && $item != '.' && $item != '..') {
       echo "Found Folder $newPath<br>";
       readDirs($newPath);
    }
    else{
      echo '&nbsp;&nbsp;Found File or .-dir '.$item.'<br>';
    }
  }
}

$path =  "/";
echo "$path<br>";

readDirs($path);

Use RecursiveDirectoryIterator in conjunction with RecursiveIteratorIterator.

$di = new RecursiveDirectoryIterator('path/to/directory');
foreach (new RecursiveIteratorIterator($di) as $filename => $file) {
    echo $filename . ' - ' . $file->getSize() . ' bytes <br/>';
}

You probably want to use a recursive function for this, in case your sub directories have sub-sub directories

$main = "MainDirectory";

function readDirs($main){
  $dirHandle = opendir($main);
  while($file = readdir($dirHandle)){
    if(is_dir($main . $file) && $file != '.' && $file != '..'){
       readDirs($file);
    }
    else{
      //do stuff
    }
  } 
}

didn't test the code, but this should be close to what you want.