Stdlib: dirname, basename, and realpath for multi-file apps

[PurHur]

Problem

Multi-file web apps resolve templates with __DIR__ includes (#85) and need path builtins for guards:

$tpl = __DIR__ . '/../templates/home.php';
if (is_file($tpl)) { include $tpl; }

examples/003-MiniWebApp uses __DIR__ only today; dirname / realpath are still missing from ext/standard/Module.php for portable config loading.

Goal

dirname, basename, and realpath with PHP semantics on VM; JIT string paths where arguments are compile-time literals; AOT via libc realpath(3) FFI or VM fallback.

Implementation hints

Builtin	VM	JIT	Registration
dirname	Pure string (PHP rules for / and .)	Literal fold when arg is const string	ext/standard/dirname.php
basename	Same	Literal fold	ext/standard/basename.php
realpath	realpath() native or FFI	Call libc when path is literal	ext/standard/realpath.php

Step	Files
1	Add PHP implementations under ext/standard/
2	Register in ext/standard/Module.php
3	JIT handlers in lib/JIT/Builtin/ (or VM-only first)
4	test/compliance/cases/stdlib_dirname.phpt, stdlib_realpath_missing.phpt
5	script/capability-matrix.php rows

Interaction with web stack

• Language: include/require in JIT and AOT (multi-file applications) #54 / Language: JIT include/require compile-time lowering (#54 follow-up) #475 — include paths; realpath before include for security
• AOT: PHPC_DEPLOY_ROOT for runtime template includes in deployed binaries #585 / AOT: Runtime include() of deploy-root PHP via phpc_deploy_path() #623 — deploy-root paths may make realpath redundant for templates; still needed for upload dirs
• Stdlib: file_get_contents and readfile for templates/assets #62 — file_get_contents on resolved paths

Acceptance criteria

./script/ci-fast.sh --filter 'dirname|realpath'
docker run --rm -v "$(pwd):/compiler" -w /compiler php-compiler:22.04-dev \
  php bin/vm.php -r 'echo dirname("/var/www/public/index.php");'
# /var/www/public

PHPT: realpath returns false on missing path (PHP semantics).

Verification

Local/Docker only — not GitHub Actions.

Dependencies

• Language: Magic constants __DIR__, __FILE__, __LINE__ for multi-file apps #85 — __DIR__ / __FILE__
• Language: include/require in JIT and AOT (multi-file applications) #54 — include/require

Related

• ROADMAP 🗺️ ROADMAP: Compile a small PHP web application (living document) #78 Phase 2 Stdlib
• examples/003-MiniWebApp/templates/