search() exception when specifing a complex "sort"

[lifo101]

I can not apply a sort using the Elasticsearch\Client::search method as outlined below. The bug appears to be in AbstractEndpoint::convertArraysToStrings and it incorrectly attempts to implode() any nested array into a comma separated list but the 'sort' search criteria can be a simple string or another nested array of parameters.

$es = new Elasticsearch\Client();
print_r($es->search(array(
    'index' => 'my_index',
    'type' => 'my_type',
    'sort' => array(
        // 'aFieldName', // this would work ... the next line doesn't
        'dateCreated' => array( 'order' => 'desc' ),
    ),
    'body' => array(
        'query' => array(
            'query_string' => array(
                'query' => 'search term'
            )
        )
    )
)));

[polyfractal]

Thanks for the report! Looks like this would have affected other "complex" parameters like filter or facet. Bug fixed and a few tests added. Let me know if you run into any more problems!