Symphony.

Sorry, this is a bit of a Noob question. I am thinking of using Symphony CMS to connect to an API which only supports POST requests even when retrieving data. Do dynamic datasources support this out of the box?

Nah, it's GET by default. To do a POST you'd have to add the curl option into /symphony/lib/toolkit/data-sources/datasource.dynamic_xml.php at line 86

$ch->setopt('CURLOPT_POST', true);

Editing the core isn't a good idea though, so you could make an extension of it. I have a CSV datasource extension I created from work by @brentburgouyne on github. You could use it as an example.

Thanks designermonkey!