Predis is a flexible and feature-complete PHP client library for Redis. This is a maintenance release for the 0.6 series exclusively aimed to fix a bug introduced in v0.6.4 when reading zero-length bulk replies from the server. For a complete list of the new features introduced in Predis v0.6.4 you can read the related release notes.
Due to a minor change introduced in Predis v0.6.4 that was not covered by any test, zero-length bulk replies were being incorrectly handled, which resulted in protocol desynchronization errors. Here is a snippet to reproduce the issue with v0.6.4:
$redis->set('foo', '');
$foo1 = $redis->get('foo'); // correct value returned, but wrong protocol handling
$foo2 = $redis->get('foo'); // desynchronization error ensues with the successive read op.
Thanks to Jordi Boggiano for quickly spotting the above-mentioned bug and providing a patch to fix the issue.