PHP Manual: SolrQuery::addExpandSortField

public function SolrQuery::addExpandSortField(string $field, string $order = ?): SolrQuery

Orders the documents within the expanded groups (expand.sort parameter).

field

field name

order

Order ASC/DESC, utilizes SolrQuery::ORDER_* constants.

Default: SolrQuery::ORDER_DESC

SolrQuery::setExpand() - Enables/Disables the Expand Component
SolrQuery::removeExpandSortField() - Removes an expand sort field from the expand.sort parameter
SolrQuery::setExpandRows() - Sets the number of rows to display in each group (expand.rows). Server Default 5
SolrQuery::setExpandQuery() - Sets the expand.q parameter
SolrQuery::addExpandFilterQuery() - Overrides main filter query, determines which documents to include in the main group
SolrQuery::removeExpandFilterQuery() - Removes an expand filter query

SolrQuery::addExpandSortField