The toolchain for HHVM is all installed as a single big deliverable, which gives you the language engine and supporting runtime libraries itself, an in-address-space web server (Facebook's Proxygen), a debugger in the form of hhvm -a, and the Hacklang toolchain accessed via hh_client and appropriate editor/IDE integrations.
I share your intuition that there is actually a glittering core of "stuff-that-makes-you-successful" hiding in the incidental complexity of PHP, and we wrote this blog post trying to put some substance behind that intuition: https://slack.engineering/taking-php-seriously-cf7a60065329