fix(php8): resolve deprecation warning for urlencode() in PHP 8+

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.0.2] - 2024-09-20
+
+### Fixed
+
+- Fixed a deprecation warning in PHP 8+ for `urlencode()`. The `client_id` and `client_secret` parameters in the constructor of `OpenIDConnectClient` were updated to default to an empty string (`''`) instead of `null`. This resolves issues where passing `null` to `urlencode()` would trigger a deprecation warning in PHP 8+.
+
 ## [1.0.1] - 2024-09-13
 
 ### Fixed

src/OpenIDConnectClient.php

@@ -880,6 +880,8 @@ protected function requestTokens(string $code, array $headers = []) {
         $authorizationHeader = null;
         # Consider Basic authentication if provider config is set this way
         if ($this->supportsAuthMethod('client_secret_basic', $token_endpoint_auth_methods_supported)) {
+            $this->clientID = $this->clientID ?? '';
+            $this->clientSecret = $this->clientSecret ?? '';
             $authorizationHeader = 'Authorization: Basic ' . base64_encode(urlencode($this->clientID) . ':' . urlencode($this->clientSecret));
             unset($token_params['client_secret'], $token_params['client_id']);
         }