PHP Performance Explained: How Opcache, JIT, and AOT Compilers Actually Work

PHP processes every request by parsing source files, compiling them into opcodes, and executing them via the Zend VM — discarding all that work when the request ends. Opcache addresses this by caching compiled opcodes in memory, eliminating redundant re-parsing and delivering the single largest performance gain available to PHP applications at minimal cost. JIT compilation goes further by converting frequently executed code into native machine code at runtime, though its benefits are largely limited to computation-heavy workloads rather than typical web requests. Ahead-of-time (AOT) compilation, as demonstrated by the Swoole team's open-source TypePHP project, takes a different approach by compiling PHP directly into a standalone native binary before deployment, bypassing the need for a PHP interpreter entirely. Unlike the first three techniques, AOT requires trade-offs in language flexibility but opens the door to entirely new use cases for PHP beyond traditional web applications.