filp/whoops · error · InvalidArgumentException

Argument to Whoops\Handler\CallbackHandler::__construct must

Error message

Argument to Whoops\Handler\CallbackHandler::__construct must be valid callable

What it means

Error "Argument to Whoops\Handler\CallbackHandler::__construct must be valid callable" thrown in filp/whoops.

Source

Thrown at src/Whoops/Handler/CallbackHandler.php:30

 * Wrapper for Closures passed as handlers. Can be used
 * directly, or will be instantiated automagically by Whoops\Run
 * if passed to Run::pushHandler
 */
class CallbackHandler extends Handler
{
    /**
     * @var callable
     */
    protected $callable;

    /**
     * @throws InvalidArgumentException If argument is not callable
     * @param  callable                 $callable
     */
    public function __construct($callable)
    {
        if (!is_callable($callable)) {
            throw new InvalidArgumentException(
                'Argument to ' . __METHOD__ . ' must be valid callable'
            );
        }

        $this->callable = $callable;
    }

    /**
     * @return int|null
     */
    public function handle()
    {
        $exception = $this->getException();
        $inspector = $this->getInspector();
        $run       = $this->getRun();
        $callable  = $this->callable;

        // invoke the callable directly, to get simpler stacktraces (in comparison to call_user_func).

View on GitHub (pinned to fa1bc9c95a)

When it happens

Trigger: Thrown at src/Whoops/Handler/CallbackHandler.php:30 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of filp/whoops@fa1bc9c95a (2026-08-21). Data as JSON: /api/errors/53fe1ff4fa1e49bb. Report an issue: GitHub.