The HipHop Virtual Machine

Introduced the HipHop Virtual Machine (HHVM) as a dynamic translation engine for PHP, offering a faster alternative to the HipHop interpreter (hphpi) and aiming to eventually replace static compilation for all PHP execution. HHVM uses a high-level stack-based virtual machine executing HipHop Bytecode (HHBC) and employs a 'tracelet' approach for JIT compilation, limiting traces to single basic blocks with type guards. This approach showed significant performance gains over hphpi and is expected to approach or exceed static compilation performance.