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/FilterHandler.php:158

            }
        }

        if (\count($filtered) > 0) {
            $this->getHandler($filtered[\count($filtered) - 1])->handleBatch($filtered);
        }
    }

    /**
     * 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/FilterHandler.php:158 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/49d34a29dcc36d76. Report an issue: GitHub.