(PECL solr >= 0.9.2)
SolrQuery::getFacetSort — Returns the facet sort type
$field_override = ?): intReturns an integer (SolrQuery::FACET_SORT_INDEX or SolrQuery::FACET_SORT_COUNT)
field_overrideThe name of the field
Returns an integer (SolrQuery::FACET_SORT_INDEX or SolrQuery::FACET_SORT_COUNT) on success or null if not set.