I will re-jiggle this plus dependent test cases later tonight. The reason for this change was to test _ignoring of `undefined`_ values. If add a key such that:

```
headers: {
    hello: undefined
}
```

The key `hello` should be missing from the request header. But this PHP script returns an empty string for that key (provided that the key is in the query string). I can try and re-work this though.