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# Facebook\Helpers\FacebookJavaScriptHelper
If you're using the [JavaScript SDK](https://developers.facebook.com/docs/javascript) on your site, information on the logged in user is stored in a cookie. Use the `FacebookJavaScriptHelper` to obtain an access token or signed request from the cookie.
## Usage {#usage}
This helper will handle validating and decode the signed request from the cookie set by the JavaScript SDK.
~~~
$fb = new Facebook\Facebook([/* */]);
$jsHelper = $fb->getJavaScriptHelper();
$signedRequest = $jsHelper->getSignedRequest();
if ($signedRequest) {
$payload = $signedRequest->getPayload();
var_dump($payload);
}
~~~
If a user has already authenticated your app, you can also obtain an access token.
~~~
$fb = new Facebook\Facebook([/* */]);
$jsHelper = $fb->getJavaScriptHelper();
try {
$accessToken = $jsHelper->getAccessToken();
} catch(Facebook\Exceptions\FacebookResponseException $e) {
// When Graph returns an error
echo 'Graph returned an error: ' . $e->getMessage();
} catch(Facebook\Exceptions\FacebookSDKException $e) {
// When validation fails or other local issues
echo 'Facebook SDK returned an error: ' . $e->getMessage();
}
if (isset($accessToken)) {
// Logged in.
}
~~~
You will likely want to make an Ajax request when the login state changes in the Facebook SDK for JavaScript. Information about that here: [FB.event.subscribe](https://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus/#events)
## Instance Methods {#instance-methods}
### __construct() {#construct}
~~~~
public FacebookJavaScriptHelper __construct(FacebookApp $app, FacebookClient $client, $graphVersion = null)
~~~~
Upon instantiation, `FacebookJavaScriptHelper` validates and decodes the signed request that exists in the cookie set by the JavaScript SDK if present.
### getAccessToken() {#get-access-token}
~~~
public Facebook\AccessToken|null getAccessToken( Facebook\FacebookClient $client )
~~~
Checks the signed request for authentication data and tries to obtain an access token access token.
### getUserId() {#get-user-id}
~~~
public string|null getUserId()
~~~
A convenience method for obtaining a user's ID from the signed request if present. This will only return the user's ID if a valid signed request can be obtained and decoded and the user has already authorized the app.
~~~
$userId = $jsHelper->getUserId();
if ($userId) {
// User is logged in
}
~~~
This is equivalent to accessing the user ID from the signed request entity.
~~~
$signedRequest = $jsHelper->getSignedRequest();
if ($signedRequest) {
$userId = $signedRequest->getUserId();
// OR
$userId = $signedRequest->get('user_id');
}
~~~
### getSignedRequest() {#get-signed-request}
~~~
public Facebook\SignedRequest|null getSignedRequest()
~~~
Returns the signed request as a [`Facebook\SignedRequest`](/docs/php/SignedRequest) entity if present.
### getRawSignedRequest() {#get-raw-signed-request}
~~~
public string|null getRawSignedRequest()
~~~
Returns the raw encoded signed request as a `string` or `null`.