How can unlink () find the file to delete?

My application has a field " Photo

" to store the url. It uses sfWidgetFormInputFileEditable

widgets for the layout. To remove the old image when loading a new image, I use unlink before setting the value in the redirected setter and it works !!!

if (file_exists($this->_get('photo')))
    unlink($this->_get('photo'));

      

        
        
        
      

    

• Photos are saved in files uploads / photos and when saving ' Photo
  
  ' only the filename xxx-yyy.zzz
  
  (not the full path) is saved . However, I want to know how does symfony / php know the full path of the file to be deleted?

Part 2: I use sfThumbnailPlugin

to create sketches. So the actual code looks like this:

public function setPhoto($value)
    {   
        if(!empty($value))
            {
                Contact::generateThumbnail($value); // delete current Photo & create thumbnail
                $this->_set('photo',$value);    // setting new value after deleting old one
            }
    }   

    public function generateThumbnail($value)
    {
                $uploadDir = sfConfig::get('app_photo_upload'); // path to upload folder
                if (file_exists($this->_get('photo')))
                {
                  unlink($this->_get('photo')); // delete full-size image
                  // path to thumbnail
                  $thumbpath = $uploadDir.'/thumbnails/'.$this->get('photo'); 
                  // read a blog, tried setting dir manually, doesn't work :(
                  //chdir('/thumbnails/');
                  // tried closing the file too, doesn't work! :(
                  //fclose($thumbpath) or die("can't close file"); 
                  //unlink($this->_get('photo'));   // doesn't work; no error :( 
                  unlink($thumbpath);   // doesn't work, no error :(
                }

                 $thumbnail = new sfThumbnail(150, 150);
                 $thumbnail->loadFile($uploadDir.'/'.$value);
                 $thumbnail->save($uploadDir.'/thumbnails/'.$value, 'image/png');
    }

      

        
        
        
      

    

2. Why can't I remove a thumbnail using the unlink () function? ops sequence is incorrect? Is it because the old thumbnail is showing in the widget sfWidgetFormInputFileEditable
   
   ?

I spent hours trying to figure this out, but couldn't cover up the real reason. Thanks in advance.