There is no build command

A transpiler should be invisible. There is no watcher to start and no command to remember: the engine compares the modification times of your sources against the built app and rebuilds only when something is newer.

$lastBuild = file_exists($this->appFile) ? filemtime($this->appFile) : 0
foreach ($checkFiles AS $file) filemtime($file) > $lastBuild && $changes[] = basename($file)
if (!$changes) return

Edit, refresh, done. The loop feels interpreted while what actually runs stays compiled.

The detail that makes it trustworthy is the check afterwards. Generated PHP goes through php -ln before it is allowed to replace anything, so a parse error surfaces as a highlighted source page anchored on the line, rather than as a half-written file the next request tries to run.

The boundary is worth being honest about. Rebuilding writes files during a request, which is fine on a machine you are editing and wrong on one serving traffic, so production takes a different path.

Three debugging routes come with it, and they say what kind of tool this is meant to be: /phlo/source shows the original, /phlo/nodes shows the parsed tree, /phlo/build shows the generated PHP. A compiler you are asked to trust without being able to look inside it is a compiler you will eventually fight.