Note - if using morelikethis, and your query is on a numeric ID, then you will not be able to access the moreLikeThis object in the results...
when q=id:3493 searching with mlt, result is:
SolrObject Object
(
...
    [moreLikeThis] => SolrObject Object
        (
            [3493] => SolrObject Object
                (
                    [numFound] => 6286
                    [start] => 0
                    [docs] => Array
                        (
....etc
the numeric object name (3493 above) is impossible to access
not by $response->moreLikeThis->{3493} nor $response->moreLikeThis->{'3493'}, nothing...
only way is to convert the moreLikeThis object into an array with:
$response_array = (array) $response->moreLikeThis;
then iterate the array as the array key is known.