PIE (PHP Installer for Extensions) is a CLI tool designed to replace PECL for installing PHP extensions. It downloads, builds (or downloads precompiled binaries), installs, and manages PHP extensions across Unix, macOS, and Windows platforms. The tool is distributed as a PHAR and integrates deeply with Composer for dependency resolution, package metadata, and installation workflows. Its architecture is modular, using Symfony Console for command handling, a custom DI container (Illuminate Container), and a variety of strategy patterns for platform-specific operations (e.g., INI configuration methods like phpenmod, docker-php-ext-enable, standard ini). It also includes self-update functionality with cryptographic attestation verification via GitHub CLI or OpenSSL, and supports system dependency auto-installation through package managers (apt, dnf, apk, brew). The codebase exhibits strong engineering practices: extensive unit and integration tests, Behat behavior specifications, static analysis, mutation testing, and Docker-based e2e tests across multiple Linux distributions. While many internal classes are marked @internal, the interfaces and value objects are clean and well-separated, demonstrating a high degree of craftsmanship. The project is actively maintained and appears to be the official future of PHP extension installation.