Building a Custom SAPI - How PHP Actually Talks to the Outside World

Thu, 30 Jul 2026 20:18:00 -0700

If you’ve only ever run PHP behind nginx, you’ve probably never had to think about how echo reaches a socket. When you embed PHP like ePHPm does, it’s the first thing you have to answer. The answer is a SAPI. There is very little written about implementing one. Most of what I know came from reading sapi/cli, sapi/cgi and sapi/embed in php-src. Then I found out which parts I’d misread. This is the write-up I wanted back in March.

Php Internals on Luther Monson

Building a Custom SAPI - How PHP Actually Talks to the Outside World