appserver.io is a multithreaded application server for PHP. Applications can be installed using drag and drop. It has outstanding performance, with benchmarking on nginx showing that it is about 50% faster than nginx alone (based on a standard Magento installation) with no additional tweaks.
Zato is an Enterprise Service Bus (ESB) and app server written by pragmatists for pragmatists. It provides an HA load-balancer, hot-deployment, and hot-reconfiguration almost everywhere (forget server restarts). It has a browser-based GUI, CLI, and API (forget XML configuration). It supports many protocols, industry standards, and data formats, including HTTP, JSON, SOAP, REST, AMQP, JMS WebSphere MQ, ZeroMQ, Redis, SQL, and FTP.