PHP at the Edge: Running the biggest CMS on the Web with WASM

Fellyph Cintra - Automattic

What happens when you compile PHP to WebAssembly and run the entire PHP CMS directly in the browser, Node.js, or any other JavaScript runtime? You get WordPress Playground, a project that pushes the boundaries of what is possible with PHP WASM.

In this talk, we will explore a technical deep dive into how we made complex server-side software run flawlessly in a client-side sandbox environment. We’ll discuss our journey through significant architectural hurdles and share how we solved core “PHP to WASM” challenges to deliver a robust, offline-capable, and highly portable runtime.

During the session, we will cover:

• Overcoming Technical Constraints: A look into our struggles and solutions involving Asyncify and JSPI, how we handle loopback requests, networking, and our journey implementing complex filesystem locks and multi-worker SQLite.
• Advanced PHP.WASM Capabilities: We’ll dive into how we brought native-like features to the browser, including dynamic PHP extensions, proc_open(), shell access, streaming, message passing, and environment variables.
• Empowering the Modern Developer Ecosystem: Discover how Playground supports testing multiple PHP and WordPress versions in real-time. We’ll show developers how to instantly preview branches and Pull Requests, use a custom build system (Blueprints), run dedicated PHP tooling (like PHPCS and PHPUnit), and use GitHub Actions to preview PRs directly in the browser.

This talk is a deep dive into the technical struggles and wins of pushing PHP WASM to its absolute limits, transforming how we ship and interact with web infrastructure in a cross-origin, offline-ready world.