https://onlinephp.io/benchmarks
It is clear to see how PHP evolved during the years. PHP 4 was fast, but lacked a lot of features that got implemented in PHP 5.0. These features made PHP 5.0 slower. PHP 5.1, 5.2 and 5.3 got optimized and are about 75% faster than 5.0. A substantial gap can be seen between PHP 5.3 and PHP 5.4, where another 30% was shaved off. And the biggest gap is between PHP 5.6 and PHP 7.0 where huge optimizations made PHP about 400% faster. Since PHP 7.0 and PHP 8.1 gains have been marginal, where PHP 8.1 is only about 20% faster than 7.0. Have we reached the ultimate speed? Or can we expect other massive optimizations in the future?