Array keys are not the same for the first time.

[fagyikaa]

In my project i create a new object and add it to one of my entity's arraycollection then persist and flush these. Then in the same request i do some more work and want to get back my newly added object with a custom method which didn't worked until i repeated the process.
I realised that the keys of the collection were not the same for the first and the other requests.
When firstly adds an element to the array collection then the keys starts from 0.
After in new requests the keys starts from 1.
I think the indexes should be always the same.