going from json_decode to insert_batch

Yes, $Arr[0]=null which is correct. But $Arr[1]
(which in my C way of thinking) is analagous to $Arr['BusinessC_0'] should be the word "choose". Can I access those array indexes either numberically or by the index name? I don't get why $Arr[1]=null?

$Arr = {array} [71]
Date_0 = ""
BusinessC_0 = "choose"
Project_0 = "choose"
Activity_0 = "choose"
RecordId_0 = "0"
Date_1 = ""
BusinessC_1 = "choose"
Project_1 = "choose"
Activity_1 = "choose"
RecordId_1 = "0"
Date_2 = ""
BusinessC_2 = "choose"

proof that an old dog can learn new tricks