This PR adds a "get-pkce-access-token" script that shows how to get an access token or refresh an access token when using a public client type with PHP.
tested both getting and refreshing tokens
tested each other sample after using the get token script to obtain a new access token
This PR adds a "get-pkce-access-token" script that shows how to get an access token or refresh an access token when using a public client type with PHP.