# Phel Lang > Building applications WITH Phel (Lisp that compiles to PHP). Triggers on .phel files, phel-config.php, phel CLI commands (init, run, repl, test, build), or requests to build a Phel app. Skip when working on the Phel compiler internals (use compiler-guide or phel-patterns instead). Use when this capability is needed. - Skill: `tomevault-io/phel-lang` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/phel-lang` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/phel-lang/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/phel-lang --- # Phel Lisp dialect compiling to PHP. PHP interop via `php/` prefix. ## Load order 1. `.agents/RULES.md` — hard rules, modern features, CLI cheatsheet 2. `.agents/tasks/common-gotchas.md` — read BEFORE writing code 3. `.agents/index.md` — task map 4. `.agents/tasks/.md` — recipe for current task 5. `.agents/quick-syntax.md` — one-screen syntax cheatsheet 6. `src/phel/` and `docs/` only when a recipe points there ## Hard rules (skim, then load RULES.md) - Verify fn names with `(doc )` or grep `src/phel/core/`. Never invent. - Collections immutable. `(conj v x)` returns new; rebind via `def`/`let`/`atom`. - CLI args: `*argv*`, not `php/$argv`. - Side effects: `doseq`; building sequences: `for`. - String module is `phel.string` (was `phel.str` pre-v0.33). - Namespace separator: prefer `.` (`app.main`); `\` deprecated. - Hot or public `defn`: add `:tag` to params + return. See `.agents/tasks/typed-defn.md`. - Opt-in `defn` metadata: `^:async`, `^:memoize`, `^{:memoize-lru N}`. - Top-level side effects break `phel build`; guard with `(when-not *build-mode* ...)`. ## Working examples `.agents/examples/{todo-app, http-json-api, cli-wordcount}/` — copy, adapt, run. --- > Source: [phel-lang/phel-lang](https://github.com/phel-lang/phel-lang) — distributed by [TomeVault](https://tomevault.io).