It would be helpful if you would specify php client, libcouchbase and server versions, describe your setup and tell more about your use case. Your log says there was a coredump, could you show the details of it?
PHP client is 2.4.6 (stable), API Version 2.3.0 (stable)
Server is 5.0.0-3519 community and libcouchbase is 2.8.7-1 16.04/xenial
The machine is on Ubuntu 16.04 LTS.