PHP OAuth with Reddit - php

Question

I'm trying to enable "oauth" for Reddit and I'm following the instructions given here - https://github.com/reddit/reddit/wiki/OAuth2
It's all good until I need to make a request for the "access_token".
The documentation says I need to make a "POST" request to the following URL
https://ssl.reddit.com/api/v1/access_token
With the following as POST DATA
grant_type=authorization_code&code=CODE&redirect_uri=URI
It also says
You must supply your OAuth2 client's credentials via HTTP Basic Auth for this request. The "user" is the client_id, the "password" is the client_secret.
And I'm not sure what above means. I've tried a number of different approaches but I'm still getting 401 error. Here's my "POST" code
$data = array('client_id' => self::CLIENT_ID,
'client_secret' => self::CLIENT_SECRET,
'grant_type' => 'authorization_code',
'code' => $_GET['code'],
'redirect_uri' => $my_redirect_url);
$response = Requests::post(self::GET_OAUTH_TOKEN_URL, array(), $data);
any ideas?

Answer 1

You need to additionally provide an "Authorization" header in this format:
"Basic %base_64_encoded_string%"
That base 64 string starts out as "username:password" or in this case "clientid:clientsecret", and then you encode it. So your Authorization header value would end up looking something like this:
"Authorization: Basic d2hhdCB1cCBob21leSBn"