yii怎么手动生成错误日志

'errorHandler' => [
            'errorAction' => 'site/error',
        ]

'errorHandler' => [
            'errorAction' => 'error/error',
        ]

public function actionError(){
       $error = \Yii::$app->errorHandler->exception;
       $error_msg = '';
       if($error){
           $filed = $error->getFile();  //获取错误文件
           $line = $error->getLine();   //获取错误行数
           $message = $error->getMessage(); //获取错误消息
           $code = $error->getCode();   //获取错误码

           $log = new FileTarget();
           $log->logFile = \Yii::$app->getRuntimePath() . "/log/error.log"; //生成文件到log目录下

           $error_msg = $message ." [file:{$filed}][line:{$line}][message:{$message}][code:{$code}][url:{$_SERVER['REQUEST_URI']}][POST_DATA:".http_build_query($_POST)."]";

           $log->messages[] = [
               $error_msg,
               1,
               'applicition',
               microtime( true )
           ];
            $log->export();
       }
       return $error_msg;
   }