// Before $payload = json_encode($response); $data = json_decode($input, true); $ok = json_validate($input); // After $payload = fastjson_encode($response); $data = fastjson_decode($input, true); $ok = fastjson_validate($input); That's the migration. Search-and-replace json_* for fastjson_*. JSON flags, error constants, and last-error semantics carry across byte-for-byte. The two extensions sit next to each other in the same process; adoption is per call site, not per repo. On the simdjson_php canonical 14.8 MB corpus, that swap buys 6.06× encode throughput, 2.66× decode, and 5.10× validate against ext/json on the same PHP 8.6.0-dev build. The repo is at github.com/iliaal/fastjson. 0.3.0 shipped yesterday. Why drop in faster JSON for PHP ext/json is fine. It's correct, well-maintained, and tracks the spec. On low-traffic endpoints it isn't on anyone's profiler. The cost shows up at scale: any application that calls json_encode and json_decode on every request path eventua...