This repository contains the code snippets from the accompanying blog post: https://hbgl.dev/detecting-cyclic-arrays-in-php-a-new-approach/
The file functions.php contains are a couple of functions that can detect cyclic arrays to various degrees of success. If you are just looking for a good working implementation, use is_cyclic_count.
composer run test
Please note that the test case Is cyclic marker with data set "Bomb" is intended to fail. I left it in there to illustrate that the particular function does not work correctly.
composer run bench
The benchmarks paint a clear picture. The winner is the count variant, especially when it comes to larger arrays. I also benchmarked the marker variant for illustration purposes, even though the implementation is fundamentally broken (see why). Benchmarks were only run on a subset of arrays that can be successfully checked by all implementations.