Check availability of igbinary

http://couchbase.com/forums/thread/igbinary-php-client reports

I'm a long time memory memcached user, and I always compiled the memcached-php extension to have igbinary. I followed the instructions to get source and unfortunately I was not able to pull the repo. Is there a version that has igbinary configured?
phpinfo reports the igbinary serializer is not avaliable in your default version.
Am I better of using the stock serializer?
Memcached::OPT_SERIALIZER
Specifies the serializer to use for serializing non-scalar values. The valid serializers are Memcached::SERIALIZER_PHP or Memcached::SERIALIZER_IGBINARY. The latter is supported only when memcached is configured with --enable-memcached-igbinary option and the igbinary extension is loaded.
Type: integer, default: Memcached::SERIALIZER_PHP.

we should look into enabling igbinary for the pre-1.8 SDKs as well it's feasibility for the >= 1.8 SDKs that are based on libcouchbase.