src/PayPalRestApiClient/Repository/AccessTokenRepository.php
public function getAccessToken($clientId, $secret)
    {
        $request = $this->client->createRequest(
            'POST',
            $this->baseUrl.'/v1/oauth2/token',
            array(
                'Accept' => 'application/json',
                'Accept-Language' => 'en_US',
                'Content-Type' => 'application/x-www-form-urlencoded'
            ),
            'grant_type=client_credentials',
            array(
                'auth' => array($clientId, $secret),
                'debug' => $this->debug
            )
        );

        $response = $this->send($request, $acceptedStatusCode = 200, 'Error requesting token:');
        $data = json_decode($response->getBody(), true);

        $builder = new AccessTokenBuilder();

        return $builder->build($data);
    }
public function getAccessToken($clientId, $secret)
    {
        $request = $this->client->createRequest(
            'POST',
            $this->baseUrl.'/v1/oauth2/token',
            array(
                'Accept' => 'application/json',
                'Accept-Language' => 'en_US',
                'Content-Type' => 'application/x-www-form-urlencoded'
            ),
            'grant_type=client_credentials',
            array(
                'auth' => array($clientId, $secret),
                'debug' => $this->debug
            )
        );

        $response = $this->send($request, $acceptedStatusCode = 200, 'Error requesting token:');
        $data = json_decode($response->getBody(), true);

        $builder = new AccessTokenBuilder();

        return $builder->build($data);
    }
Returns an access token object if paypal accepts the given credential

For the time being, expires_in is not taken into consideration.
Calling twice the getAccessToken method with the same credential will give you two different token.

@param string $clientId not null
@param string $secret not null

@return PayPalRestApiClient\Model\AccessToken