According to the RFC, the version number is stored in the 4 most-significant bits of the `time_hi_and_version` field.  When you have a hexadecimal representation, the version is found in the 14th character: `xxxxxxxx-xxxx-Vxxx-xxxx-xxxxxxxxxxxx`.  For example, if your UUID is `456daefb-5aa6-41b5-8dbc-068b05a8b201`, the version is `string(1) "4"`.

In UuidValidator lines 62-63, **we check if that 14th character matches any of the constant values**.  Therefore I figured it made sense to compare strings to strings.

Although, I didn't set the `strict` parameter of `array_search` to true, so maybe this is a moot point.  Perhaps I should make that change.  Thoughts?