chb
Lightweight on-disk hash table for fast key-value storage in pure PHP
...Bucket count and record size are configurable at file creation time, allowing CHB to be tuned for different workloads while preserving a simple and deterministic layout.
The format is page-oriented (4 KiB aligned), easy to inspect, recover, and implement, requiring no complex trees, transactions, or variable-length record management. Deleted records can be recycled within their bucket chains, reducing fragmentation without introducing free-list complexity.
CHB is ideal for caches, kv stores, indexes where low implementation complexity is more important than full database features.