在不使用小部件的情况下将图像存储在表的blob yii框架中

in my controller I have :

$model->attributes=$_POST['Societes'];
                    $file=CUploadedFile::getInstance($model,'logo');
                    $extension = $file->getExtensionName();
                    $filename = md5_file($file->tempName);
                    $fullFilename = $filename . '.' . $extension;            
                    $model->logo=$fullFilename;
                    if($model->save()) 
                    {                       
                      $file->saveAs(Yii::app()->basePath . '/../images/' . $fullFilename);  
                      $this->redirect(array('view','id'=>$model->id));

In my view I have :

<input type="file" id="id_photo" name="photo">

Running this I get this error :

Call to a member function getExtensionName() on a non-object