<?php
include "bootstrap.php";
$options = array
(
'hostname' => SOLR_SERVER_HOSTNAME,
'login' => SOLR_SERVER_USERNAME,
'password' => SOLR_SERVER_PASSWORD,
'port' => SOLR_SERVER_PORT,
'path' => SOLR_SERVER_PATH
);
$client = new SolrClient($options);
$query = new SolrQuery('*:*');
$func = new SolrCollapseFunction('field_name');
$func->setMax('sum(cscore(),field(some_other_field))');
$func->setSize(100);
$func->setNullPolicy(SolrCollapseFunction::NULLPOLICY_EXPAND);
$query->collapse($func);
$queryResponse = $client->query($query);
$response = $queryResponse->getResponse();
print_r($response);
?>