1, question

when I was in the source code of tp5.1, when I saw registration errors and exception handling mechanism, I saw a piece of code in error.php that I didn"t quite understand

public static function appError($errno, $errstr, $errfile = "", $errline = 0)
    {
        $exception = new ErrorException($errno, $errstr, $errfile, $errline);
        if (error_reporting() & $errno) {
            //  think\exception\ErrorException
            throw $exception;
        }

        self::getExceptionHandler()->report($exception);
    }

this is the handler of error, and
I particularly don"t understand the paragraph if (error_reporting () & $errno) .

this bit operation here?