Renew tokens method for Auth0 client class

src/Auth0.php

@@ -476,6 +476,40 @@ public function exchange()
         return true;
     }
 
+    /**
+     * Renews the access token and ID token using an existing refresh token.
+     * 
+     * Scope offline_access must be declared during initial authentication in order to obtain refresh token for later token renewal.
+     * 
+     * @throws CoreException If the Auth0 object does not have access token and refresh token
+     * @throws ApiException If the Auth0 API did not renew access and ID token properly
+     * @link https://auth0.com/docs/tokens/refresh-token/current
+     */
+    public function renewTokens()
+    {
+        if (!$this->accessToken) {
+            throw new CoreException('Can\'t renew the access token if there isn\'t one valid');
+        }
+
+        if (!$this->refreshToken) {
+            throw new CoreException('Can\'t renew the access token if there isn\'t a refresh token available');
+        }
+
+        $response = $this->authentication->oauth_token([
+            'grant_type' => 'refresh_token',
+            'client_id' => $this->clientId,
+            'client_secret' => $this->clientSecret,
+            'refresh_token' => $this->refreshToken,
+        ]);
+
+        if (empty($response['access_token']) || empty($response['id_token'])) {
+            throw new ApiException('Token did not refresh correctly. Access or ID token not provided.');
+        }
+
+        $this->setAccessToken($response['access_token']);
+        $this->setIdToken($response['id_token']);
+    }
+
     /**
      * Set the user property to a userinfo array and, if configured, persist
      *