Missing required parameters, includes an invalid parameter value, parameter more than once with LinkedIn API

Question

I try to authenticate with LinkedIn API with OAuth2. Code:

if ((isset($_GET["code"])) AND (isset($_GET["state"]))) {
        $code = $_GET["code"];
        $state = $_GET["state"];

        $curl_request = curl_init();
        curl_setopt_array($curl_request, array(
            CURLOPT_RETURNTRANSFER => 1,
            CURLOPT_URL => "https://www.linkedin.com/uas/oauth2/accessToken",
            CURLOPT_POST => 1,
            CURLOPT_POSTFIELDS => array(
                grant_type => "authorization_code",
                code => "$code",
                redirect_uri => "SECRET",
                client_id => "SECRET",
                client_secret => "SECRET"
            )
        ));

        $curl_result = curl_exec($curl_request);

        var_dump($curl_result);

}

I got this message:

string(153) "{"error_description":"missing required parameters, includes an invalid parameter value, parameter more than once. : client_id","error":"invalid_request"}"

Could you help m?

Answer 1

You need to add the following header in your cURL POST call to ensure that the values you are passing in the body of your POST are interpreted correctly:

Content-Type: application/x-www-form-urlencoded

For additional info, see http://tools.ietf.org/html/rfc6749#section-4.1.3 for the actual OAuth 2.0 RFC spec.

Answer 2

Use: http_build_query

curl_setopt_array($curl, array(
            CURLOPT_HTTPHEADER => array('Content-Type: application/x-www-form-urlencoded'),
            CURLOPT_RETURNTRANSFER => 1,
            CURLOPT_URL => 'https://www.linkedin.com/uas/oauth2/accessToken',
            CURLOPT_POST => 1,
            CURLOPT_POSTFIELDS => http_build_query (array(
                client_id => "secret",
                client_secret => "secret",
                grant_type => "authorization_code",
                redirect_uri => "url",
                code => $code
            )),
        ));

Answer 3

I am weirded out by this, but I just had the same problem and when I just moved client id and secret to beginning of the POST array and everything worked. I don't even.