Note that currently, if enabling MLT results in Solr, you also need to set the MinDocFrequency and MinTermFrequency, or you will not get any results back.
<?php
$client = new SolrClient($params);
$query = new SolrQuery();
$query->setMlt(true);
$query->addField('*,score');
$query->setMltMinDocFrequency(1);
$query->setMltMinTermFrequency(1);
$query->setQuery('id:doc_10');
$result = $client->query($query);
$result->setParseMode(SolrQueryResponse::PARSE_SOLR_OBJ);
$response = $result->getResponse();
$similarDocs = $response->moreLikeThis->doc_10->docs;
?>
Hope this helps.
