Seldaek/monolog · error · RuntimeException

The factory Closure should return a HandlerInterface

Error message

The factory Closure should return a HandlerInterface

What it means

Error "The factory Closure should return a HandlerInterface" thrown in Seldaek/monolog.

Source

Thrown at src/Monolog/Handler/SamplingHandler.php:86

            }

            $this->getHandler($record)->handle($record);
        }

        return false === $this->bubble;
    }

    /**
     * Return the nested handler
     *
     * If the handler was provided as a factory, this will trigger the handler's instantiation.
     */
    public function getHandler(LogRecord|null $record = null): HandlerInterface
    {
        if (!$this->handler instanceof HandlerInterface) {
            $handler = ($this->handler)($record, $this);
            if (!$handler instanceof HandlerInterface) {
                throw new \RuntimeException("The factory Closure should return a HandlerInterface");
            }
            $this->handler = $handler;
        }

        return $this->handler;
    }

    /**
     * @inheritDoc
     */
    public function setFormatter(FormatterInterface $formatter): HandlerInterface
    {
        $handler = $this->getHandler();
        if ($handler instanceof FormattableHandlerInterface) {
            $handler->setFormatter($formatter);

            return $this;
        }

View on GitHub (pinned to 57eb102834)

When it happens

Trigger: Thrown at src/Monolog/Handler/SamplingHandler.php:86 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Seldaek/monolog@57eb102834 (2026-08-17). Data as JSON: /api/errors/7c4a6eaacec7c7c6. Report an issue: GitHub.