If you enjoy reading my blog, you could consider supporting me on Patreon. For those interested in the JIT in PHP 8, I did some benchmarks for you in real-world web application scenario. Be aware that these benchmarks don't say anything about whether the JIT is useful or not, they only show whether it can improve the performance of your average web application, or not.
If this directive is excluded, the default value is set to 0, and the JIT won't run.
In my benchmarks, I'll use several variations of JIT configuration, in order to compare the differences.