$ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, 'https://test.salesforce.com/services/oauth2/token');
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $params);

        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 60);
        curl_setopt($ch, CURLOPT_TIMEOUT, 300);

        $result = curl_exec($ch);

        curl_close($ch);

"{"error":"unknown_error","error_description":"retry your request"}"

params = array(
        'grant_type'    => 'password',
        'client_id'     => $clientId,
        'client_secret' => $clientSecret,
        'username'      => $username,
        'password'      => $password . $securityToken,
    );