what is an associative array?

I am actually on 5.6.28.  I found this article: https://aws.amazon.com/blogs/developer/d...g-for-php/

which talks about getting data from either json or a string into a format acceptable to dynamodb. They have a thing called :

Marshaling a Native PHP Array
The Marshaler also provides the marshalItem() and unmarshalItem() methods that do the same type of thing, but for arrays. This is essentially an upgraded version of the existing DynamoDbClient::formatAttributes() method.

 So if I use my $data array (which has not been made into json), I have

   $dynamodb = $sdk->createDynamoDb();
   $marshaler = new Marshaler();
   $tableName='historical-activities';
   $params = [
       'TableName' => $tableName,
       'Item' => $marshaler->marshalItem($data)
   ];
   $result = $dynamodb->putItem($params);

This gives me Marshalling error: empty strings are invalid. That is true I see a bunch of empty strings above.

Then I did a search on that error and I found:

"I'm sorry, but this means that if you have an object with empty strings, you have to prune them out prior to marshaling. That is obnoxious though, I'll give it more thought. Perhaps it would be okay for the marshaler to be configured to prune/replace empties."

proof that an old dog can learn new tricks