Highlights of PHP 8.0: JIT and Major New Features

PHP 8.0.0 is the latest major version, introducing several significant changes, many new features and performance optimizations, including named arguments, union types, attributes, constructor property promotion, match expression, null‑safe operator, JIT, and improvements to the type system, error handling, and consistency.

Below is a brief introduction of some highlights:

JIT, Just‑In‑Time compilation

The most significant feature is JIT. Its development took many years, surviving the PHP 5 and 7 major version series (the PHP 6 project was aborted), and only in March last year was it finally approved to be included in PHP 8.

JIT is a compiler strategy that represents code in an intermediate state and translates it to architecture‑dependent machine code at runtime for immediate execution. In PHP, this means JIT treats the instructions generated by the Zend VM as an intermediate representation and executes them as machine code dependent on the architecture, so the code is no longer hosted by the Zend VM but runs directly on the CPU.

Although since PHP 7.0, performance has been significantly improved through optimizations such as enhancing core data structures like HashTable, strengthening certain opcodes in the Zend VM, and continuously improving the OPCache optimizer component, these optimizations seem to have reached their limit. Now JIT, working from the bottom up, is considered the best way to further boost PHP performance.

Next episode will explain all new features of PHP 8.