Libgossamer
Library that provides most of the plumbing for the Gossamer PKI.
The code syntax is compatible with PHP 5.3+, but this is only intended for PHP 5.6+, as per WordPress's new minimum supported version.
Important
This is the low-level library. If you're looking for something you can use in one of your projects...
- (TODO: Put links to higher-level abstractions here.)