Is there any way to use voltDB in a PHP application?
It definitely seems like it have a few advantages over other Databases out there!
Absolutely.
VoltDB has added a HTTP/JSON client interface to VoltDB which is available now for preview. You can download/build from http://community.voltdb.com/getinvolved#svn
Also, a C++ client library (via same page under "Client Interfaces for Other Programming Languages") exists and will be used to create a native client library for PHP. Join the community at http://community.voltdb.com to be updated.