composer install && php index.php prints out the text that includes

FAILED QUERY
labelIds=0%3DLabelOne%261%3DLabelTwo%262%3DLabelThreeException when calling DefaultApi->fetchNotes: [0] cURL error 6: Could not resolve: some.example.api.com (Domain name not found) (see http://curl.haxx.se/libcurl/c/libcurl-errors.html)

which shows that the labelIds query parameters

• LabelOne
• LabelTwo
• LabelThree

are added to the query as labelIds=0%3DLabelOne%261%3DLabelTwo%262%3DLabelThree, but they should be labelIds=LabelOne&labelIds=LabelTwo&labelIds=LabelThree.