How to retrieve Apache Solr's current search filters?
Sounds like you're writing a module to do this?

If so, if you're implementing something like the apachesolr_query_alter(&amp;$query) hook or something like that, which gives you access to the search query, you can use 

function [getFilters][1]($name = NULL)


Note that the name parameter is optional: Returns all filters matching $name, if set; otherwise, returns all filters.