Solr 1.3 has been out for a while (http://lucene.apache.org/solr/#15+September+2008+- +Solr+1.3.0+Available) so I was wondering if you are sticking with JSON?

That message just makes the project look a bit unmaintained/out of date, like some other Solr clients, when actually this seems to be the most active PHP client for Solr....?

The simple answer: I haven't removed the todo because I haven't made a decision yet.

In my own testing I've found that serialized PHP is faster to parse than JSON, yes, but unlike the JSON output writer I can't control how named lists are handled nor can I make it map to standard class instances like I can with json_decode - So to maintain the current client API I haven't moved forward with using the serialized php output writer. My fear would be that the small difference in parse time would be outweighed by the extra work we'd have to do on the client side to produce the same output. Additionally, there have been bugs with outputting the proper string lengths in the serialization format when not using utf-8 encodings in all your data.

Issue #3 is also related to your question.

I've removed the related TODO's and decided to stick with JSON response writer. See r16

Really glad to hear it since in the Solr book I mentioned that "solr-php-client's use of JSON instead of PHP response writer highlights JSON usefulness for facilitating language agnostic communication between systems."!