Not able to genrate the accesstoken using refresh token.

Not able to genrate the accesstoken using refresh token.

Hello,

I am using the refresh token for generated access token not able create here i got the output.
I have attached code genrating the accesstoken and refresh token please check. 
Array
(
    [refresh_token] => 1000.9eb87eba7593d87bb1bf215e08e6bd77.66363d84b9319cd4864c78285d2ab41d
    [client_id] => 1000.DBP0HOVT03N617777555YGQ25PJ53Y
    [client_secret] => 85dc3dfb1ab24da6a63300ad3b256305ec7ee4f4e5
    [grant_type] => refresh_token
)