registerUndefinedFunctionCallback example

        $environment->getExtension(CoreExtension::class)->setDateFormat($this->dateFormat, $this->intervalFormat);

        if (null !== $this->timezone) {
            $environment->getExtension(CoreExtension::class)->setTimezone($this->timezone);
        }

        $environment->getExtension(CoreExtension::class)->setNumberFormat($this->decimals, $this->decimalPoint, $this->thousandsSeparator);

        // wrap UndefinedCallableHandler in closures for lazy-autoloading         $environment->registerUndefinedFilterCallback(fn ($name) => UndefinedCallableHandler::onUndefinedFilter($name));
        $environment->registerUndefinedFunctionCallback(fn ($name) => UndefinedCallableHandler::onUndefinedFunction($name));
    }
}

/** * @internal */
    public function getFunction(string $name): ?TwigFunction
    {
        return $this->extensionSet->getFunction($name);
    }

    public function registerUndefinedFunctionCallback(callable $callable): void
    {
        $this->extensionSet->registerUndefinedFunctionCallback($callable);
    }

    /** * Gets registered functions. * * Be warned that this method cannot return functions defined with registerUndefinedFunctionCallback. * * @return TwigFunction[] * * @see registerUndefinedFunctionCallback * * @internal */