I'm on my shell (ubuntu 12) and encountered a strange behaviour, which I can't explain:

> 
> var\_dump(array(1.5 => "a", 2.2 => "b", 2.5 => "c"));
> 
> 
> 

prints the following in my shell:

```
array(2) {
    [1]=>
    string(1) "a"
    [2]=>
    string(1) "c"
}

```

can someone please explain this? What happens to "b"? Why is it not printed? 
(PHP 5.3)