get extension of uploaded file in cake php - php

Question

I am using cakephp 2.1 and i am trying to upload files and how can i retrive the extension of the file.
Database/users
Id Auto_Increment
username
file_name
Controller/UsersController.php
public function register(){
if ($this->request->is('post')){
$filename = $this->data['User']['file_name']['name'];
//$temp_ext = $this->data['User']['resume_file']['ext'];
$this->Session->setFlash('Extension : ' . $temp_ext);
}
}
When tried the above code, to get extension. it only gives single letters like L, r ie firt character of the filename but not extension
Now how can i get the extension of the file.. i gone through this link
http://api.cakephp.org/class/file
but could not understand to retrieve the file.
Adding a Debug report to #Julian Hollmann
array(
'User' => array(
'file_name' => array(
'name' => '550992_234300256686731_213914803_n.jpg',
'type' => 'image/jpeg',
'tmp_name' => 'D:\xampp\tmp\php866F.tmp',
'error' => (int) 0,
'size' => (int) 42292
)
)
)

Answer 1

First of all, your data should be in $this->request->data
If you want to see what's in there, just do debug($this->request->data);
Edit:
The correct answer is:
$filename = $this->request->data['User']['file_name']['name'];
$extension = pathinfo($filename, PATHINFO_EXTENSION);
See also php manual

Answer 2

$filename = $this->data['User']['file_name']['name'];
$this->request->data['User']['file_name'] = $filename;
$fileExt = explode(".", $filename);
$fileExt2 = end($fileExt);
Try this one... it will give you extension