Encoding file in utf-8

Hi guys!
This is my action for import in my controller:

public function actionImport($id)
 	{
 	    $import = new Import();
 	    $model  = $this->findModel($id);


 		if ( Yii::$app->request->isPost )
 		{
 			$file      = UploadedFile::getInstance($import,'import_citazioni');
 			$file_path = Yii::getAlias( '' );



 			if ( null === $file )
 			{
 				Yii::$app->session->setFlash('error', Yii::t('app', 'Nessun File caricato o vuoto!'));

 				return $this->render('import', [
 					'import' => $import,
 					'model' => $model,
 				]); 
 			}


 			$filename = str_replace(' ','_', $file->baseName);
 			$urlFile  = $file_path.$filename.'.'.$file->extension;
 			$file_upload = $file->saveAs($file_path.$filename.'.'.$file->extension);





 			if($file_upload)
 			{
 				$import->importCitazioni($urlFile,$id);

 				Yii::$app->session->setFlash('success', Yii::t('app', 'File caricato correttamente!'));

 				return $this->render('import', [
 					'import' => $import,
 					'model' => $model,
 				]);

 			}

 			Yii::$app->session->setFlash('error', Yii::t('crm', 'Errore nel caricamento del File'));

 			return $this->render('import', [
 				'import' => $import,
 				'model' => $model,
 			]);

 		}

 		return $this->render('import',[
 		    'import' => $import,
 			'model' => $model,
 		]);

 	}

I need to use utf8_encode() for other file (like ISO…). What I have to do?
I try but it doesn’t match.
Thank you very much!