Part 1 covered the plumbing. ePHPm registers ephpm_kv_* and ephpm_db_* functions that call straight into Rust. A cache read through one costs about a tenth of a microsecond instead of a loopback round trip. That’s nice and also useless on its own. Nobody is going to rewrite their WordPress object cache or their Laravel cache store around a function called ephpm_kv_set(). Applications talk to existing APIs instead:

The standard way to run a WordPress site is four services:

ePHPm v0.7.0 shipped per-site multi-tenancy. Point [server] sites_dir at a directory and every Host maps to its own docroot and its own Turso database file. One process serves all of them. The first question anybody asks about that is “how many sites fit on a box?” The honest way to answer it is to turn the question around. What does one more site cost? If you know the marginal RAM, file descriptors, CPU and disk for a tenant, the box size falls out of arithmetic.

Last month I wrote about running SQLite behind a MySQL socket with litewire. I ended on “passing an install suite is not the same thing as behaving like MySQL”. That turned out to be accurate. On August 10th a few things happened at once:

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.

Most of the PHP sites I’d put on ePHPm don’t need a MySQL server. A brochure WordPress, an internal Laravel tool, a preview environment that lives for an afternoon. What they do need is something that looks like MySQL, because mysqli and pdo_mysql are the only database drivers their code has ever been pointed at. I mentioned this in the ePHPm pragmatism post as a one-paragraph “because”. This is the longer version, now that WordPress 7.0 and Laravel 13 both install and…