In PHP array keys that are integers are always kept as integer,
meaning the type of the key of `$a = ["1" => "one"]` will be integer not
string.
While are hacks to circumvent this (case std object with string keys to
an assoc. array) those hacks are performance wise awefull and also not
needed as in PHP you can always access that element with `$a[1]` or
`$a["1"]`.
So TL;DR;: do not lie about return types.
Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>
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