Can php URLs have numeric parameters?

Is this valid?:

http://www.SomeURL.com/Index.php?123=开发者_C百科xyz

Will I be able to access the value 'xyz' under the key '123' the same ways as usual?

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Yes, it's completely possible. It's also very easy to try by yourself.

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Yes you can do this.

$_GET['123']

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Yes this is something you can do.