Find function is missing, but not sure what to put in - cakephp

Question

Ok, I'm trying to File & Folder classes as specified here:
http://book.cakephp.org/2.0/en/core-utility-libraries/file-folder.html#
My Folder Controller looks like this:
<?php
App::uses('AppController', 'Controller');
App::uses('Folder', 'Utility');
App::uses('File', 'Utility');
class FolderController extends AppController {
public $uses = array();
public function display() {
$dir = '/var/www/html/letters/pdfdir/';
$files = $dir->find('.*\.pdf', true);
foreach ($files as $file) {
$file = new File($dir->pwd() . DS . $file);
$contents = $file->read();
echo 'CONTENT: '.$contents;
// $file->write('I am overwriting the contents of this file');
// $file->append('I am adding to the bottom of this file.');
// $file->delete(); // I am deleting this file
$file->close(); // Be sure to close the file when you're done
}
}
}
but I get the following error:
Error: Call to a member function find() on a non-object
File: /var/www/html/letters/app/Controller/FolderController.php
Line: 13
Any help appreciated.
Regards

Answer 1

You have a mistake
$dir = '/var/www/html/letters/pdfdir/';
should be
$dir = new Folder('/var/www/html/letters/pdfdir');
In your original code $dir is just a variable of string type. However, it should be an object of Folder class.
Another note: you have to remove the trailing slash.

Answer 2

$dir is still a string, you need to pass it to a File or Folder object to become usable as an object.