WordPress debug mode and xml-rpc problems

This post is about using xml-rpc to post in WordPress. If you experience problems of this type:

32700:parse error. not well formed


32300:transport error - HTTP status code was not 200

It can be many things, but we have been crazy checking all the configuration until we realised that the problem was coming from the fact that the WordPress installation had the WP_DEBUG flag set to TRUE

define('WP_DEBUG', 'true');

And you should change it to FALSE