diff --git a/MatomoTracker.php b/MatomoTracker.php
index 91461cf..cbb7b80 100644
--- a/MatomoTracker.php
+++ b/MatomoTracker.php
@@ -105,7 +105,7 @@ class MatomoTracker
 
     public $hasCookies = false;
 
-    public $token_auth = false;
+    public $token_auth = null;
 
     public $userAgent = false;
 
@@ -159,7 +159,7 @@ class MatomoTracker
     public $configReferralCookieTimeout = 15768000; // 6 months
 
     // Visitor Ids in order
-    public $userId = false;
+    public $userId = null;
     
     public $forcedVisitorId = false;
     
@@ -1571,11 +1571,11 @@ public function setIp(string $ip)
      *
      * A User ID can be a username, UUID or an email address, or any number or string that uniquely identifies a user or client.
      *
-     * @param string $userId Any user ID string (eg. email address, ID, username). Must be non empty. Set to false to de-assign a user id previously set.
+     * @param string|null $userId Any user ID string (eg. email address, ID, username). Must be non empty. Set to null to de-assign a user id previously set.
      * @return $this
      * @throws Exception
      */
-    public function setUserId(string $userId)
+    public function setUserId(?string $userId)
     {
         if ($userId === '') {
             throw new Exception("User ID cannot be empty.");
@@ -1674,9 +1674,9 @@ public function getIp()
      * Returns the User ID string, which may have been set via:
      *     $v->setUserId('username@example.org');
      *
-     * @return bool
+     * @return string|null
      */
-    public function getUserId()
+    public function getUserId(): ?string
     {
         return $this->userId;
     }
@@ -1743,10 +1743,10 @@ public function getAttributionInfo()
      * - force the visitor IP
      * - force the date &  time of the tracking requests rather than track for the current datetime
      *
-     * @param string $token_auth token_auth 32 chars token_auth string
+     * @param string|null $token_auth token_auth 32 chars token_auth string
      * @return $this
      */
-    public function setTokenAuth(string $token_auth)
+    public function setTokenAuth(?string $token_auth)
     {
         $this->token_auth = $token_auth;
 
@@ -2052,7 +2052,7 @@ protected function prepareStreamOptions(string $method, $data, bool $forcePostUr
     /**
      * @ignore
      */
-    protected function sendRequest(string $url, string $method = 'GET', $data = null, bool $force = false): string
+    protected function sendRequest(string $url, string $method = 'GET', $data = null, bool $force = false)
     {
         self::$DEBUG_LAST_REQUESTED_URL = $url;
 
@@ -2114,7 +2114,7 @@ protected function sendRequest(string $url, string $method = 'GET', $data = null
             curl_setopt_array($ch, $options);
             ob_start();
             $response = @curl_exec($ch);
-            
+
             try {
                 $header = '';