AI-Driven Refactoring in PHP: When to Trust Copilot (and When to Take the Wheel)

Using AI tools like Copilot for PHP refactoring carries real risks alongside productivity gains. The post covers a practical 'Prompt–Refactor–Verify' cycle, demonstrates refactoring blocking I/O to concurrent Amp-based Fibers, and identifies key AI failure modes: shared state corruption, the 'AI echo chamber' where AI writes both buggy code and passing tests, happy-path bias with silent null returns, hallucinated APIs, and architecture drift from context-blind suggestions. Countermeasures include constraint headers to enforce design rules, composition over god constructors, and a pre-merge checklist emphasizing type safety, explicit errors, and explainability. The core message: AI accelerates refactoring but multiplies mistakes—senior developers must curate, not just accept, AI output.