RoadRunner is a Go-based application server that hosts PHP workers. The framework boots once per worker; subsequent requests are served against the warm state.
It is a strong alternative to PHP-FPM for Laravel, Symfony, and Yii applications that benefit from skipping framework boot. Spiral Framework ships with RoadRunner integration.
The catch is the same as Octane: code must be aware that it lives between requests. Static state is sticky; database connections need explicit handling.