ปัญหา function getimagesize() กับ server unix .........................ช่วยด้วย

public function action_index()
	{
		$model = new Model_Manage_WImage;
		
		if ( ! empty($_POST['title']) AND ! empty($_FILES['file']['tmp_name']))
		{
			$ext = strtolower(pathinfo($_FILES['file']['name'], PATHINFO_EXTENSION));
			
			if (preg_match('/^(jpe?g|gif|png)$/i', $ext))
			{
				// make file name
				while(file_exists($file_name = Controller_Manage_WImage::WIMAGE_PATH.'img'.time().'.'.$ext));
				
				list($w, $h) = getimagesize($_FILES['file']['tmp_name']);
				$title = $_POST['title']." [{$w}x{$h}]";
				
				// save file
				move_uploaded_file($_FILES['file']['tmp_name'], $file_name);
				
				// insert to db
				$model->new_image($title, $file_name, date('Y-m-d'));
			}
		}
		
		$this->template->body = View::factory('manage/wimage')
			->set('images', $model->image_list());
	}