public function checkLogin($tokenKey, $tokenSecret, $tokenVerifier) {
		
		$this->token = new Consumer($tokenKey, $tokenSecret);
		
		// the location to send a cURL request to to obtain this user's details
		$returnUrl = $this->base.$this->loc_api.$this->loc_return.$this->format.'/';
		
		// generate a token request call using post data
		$req = Request::from_consumer_and_token($this->consumer, $this->token, "POST", $returnUrl, array(
			'oauth_token' => $tokenKey,
			'oauth_verifier' => $tokenVerifier
		));
		
		// sign the request using the specified signature/encryption method (set in this class)
		$req->sign_request($this->signature, $this->consumer, $this->token);
		
		// post the details to VATSIM and obtain the result
		$response = $this->curlRequest($returnUrl, $req->to_postdata());
		
		if ($response){
			// convert using our response format (depending upon user preference)
			$sso = $this->responseFormat($response);
			
			// did VATSIM return a successful result?
			if ($sso->request->result == 'success'){
				
				// one time use of tokens only, token no longer valid
				$this->token = false;
				
				// return the full object to the user
				return $sso;

			} else {
				
				// oauth returned a failed request, store the error details
				$this->error = array(
					'type' => 'oauth_response',
					'code' => false,
					'message' => $sso->request->message
				);
				
				return false;
				
			}
			
		} else {
			// cURL response failed
			return false;
		}
		
	}