$data = array(
    'client_id' => 'testtest',
    'client_secret' => 'TheBigSecret',
    'redirect_uri' => 'https://oa.dnc.global/web/?action=oauth',
    'grant_types' => 'authorization_code',
    'scope' => 'openid sli',
);

$h = curl_init("https://oa.dnc.global/web/http.api/json/clients/");
curl_setopt($h, CURLOPT_RETURNTRANSFER, true);
curl_setopt($h, CURLOPT_TIMEOUT, 10);
curl_setopt($h, CURLOPT_POST, true);
$data_string = json_encode($data);  
curl_setopt($h, CURLOPT_POSTFIELDS, $data_string);
curl_setopt($h, CURLOPT_HTTPHEADER, array(                                                                          
    'Content-Type: application/json',                                                                                
    'Content-Length: ' . strlen($data_string),
    'Accept: application/json')                                                    
);