What you learned

In PHP

You install PHP and Composer, you run source files directly, and a typed function will coerce "5" unless that file says strict_types. Composer's lockfile is how an app builds the same way twice. Nothing in this chapter asked you to stop doing that.

In Rust

This chapter taught five things:

1. What Rust checks — a type mismatch (E0308) or a live conflicting borrow (E0502) stops the compile; PHP often coerces until that line runs.
2. Install with rustup — one installer for rustc and cargo, confirm with rustup show.
3. Cargo — cargo new, cargo run, cargo fmt, cargo clippy, debug vs release (including overflow behaviour).
4. Dependencies and pinning — cargo add, commit Cargo.lock for apps, pin the team toolchain in rust-toolchain.toml (never rustup default nightly).
5. A small CLI — read lines, stop at EOF, test pure arithmetic with cargo test.

[dev-dependencies] is Composer's require-dev. CI should pass --locked. The site does not run those tests for you. Run them locally, or use the Playground Test action on the calculator lesson.

Key takeaways

1. rustup installs the toolchain; pin a specific stable version for the team.
2. Cargo is the everyday tool: new, run, fmt, clippy, add, test.
3. PHP coerces by default. Rust does not compile the mismatch.
4. Cargo.lock and --locked keep builds repeatable.
5. The calculator stops at EOF, and cargo test covers the arithmetic.

Take the chapter quiz from the button on this page. It opens a separate page. Thirteen questions, and you need 80% to pass. After you submit, each question shows a one-line explanation.

What's next: Variables