“Since PHP 5.5 the Opcache extension is part of the core and adds support for byte-code caching of PHP scripts. For a dynamic language such as PHP, a byte-code cache can increase the performance significantly, because it guarantees a script is compiled only once.
The default settings of the Opcache extension already boost PHP performance by a large amount, but you can tinker with the configuration settings to get even more out of it.“
https://tideways.com/profiler/blog/fine-tune-your-opcache-configuration-to-avoid-caching-suprises