diff --git a/src/Auth/AuthService.php b/src/Auth/AuthService.php
index d28391af9375e94e5882fe587e25a32fab5694bd..8ed530facbce520efad9ef4c6701ad52c08f5dba 100644
--- a/src/Auth/AuthService.php
+++ b/src/Auth/AuthService.php
@@ -80,7 +80,7 @@ class AuthService extends \JiraRestApi\JiraClient
      * @throws \Exception
      * @throws \JiraRestApi\JiraException
      */
-    public function __construct(ConfigurationInterface $configuration = null, LoggerInterface $logger = null, $path = './')
+    public function __construct(?ConfigurationInterface $configuration = null, ?LoggerInterface $logger = null, $path = './')
     {
         parent::__construct($configuration, $logger, $path);
         $this->setAPIUri($this->auth_api_uri);
diff --git a/src/Board/BoardService.php b/src/Board/BoardService.php
index 8c7c0ae9f182ef8b6f65fdc75628f7343e9ddbef..fb2c5352bed3a934b416ac158465b2fb37719e34 100644
--- a/src/Board/BoardService.php
+++ b/src/Board/BoardService.php
@@ -14,7 +14,7 @@ class BoardService extends \JiraRestApi\JiraClient
 
     private $agileVersion = '1.0';
 
-    public function __construct(ConfigurationInterface $configuration = null, LoggerInterface $logger = null, $path = './')
+    public function __construct(?ConfigurationInterface $configuration = null, ?LoggerInterface $logger = null, $path = './')
     {
         parent::__construct($configuration, $logger, $path);
         $this->setAPIUri('/rest/agile/'.$this->agileVersion);
@@ -51,13 +51,14 @@ class BoardService extends \JiraRestApi\JiraClient
      *
      * @param array $paramArray
      *
-     * @return PaginatedResult|null array of Board class
-     *@throws \JiraRestApi\JiraException
+     * @throws \JiraRestApi\JiraException
      *
+     * @return PaginatedResult|null array of Board class
      */
     public function getBoards($paramArray = []): ?PaginatedResult
     {
         $json = $this->exec($this->uri.$this->toHttpQueryParameter($paramArray), null);
+
         try {
             return $this->json_mapper->map(
                 json_decode($json, false, 512, $this->getJsonOptions()),
@@ -65,6 +66,7 @@ class BoardService extends \JiraRestApi\JiraClient
             );
         } catch (\JsonException $exception) {
             $this->log->error("Response cannot be decoded from json\nException: {$exception->getMessage()}");
+
             return null;
         }
     }
@@ -165,6 +167,7 @@ class BoardService extends \JiraRestApi\JiraClient
             );
         } catch (\JsonException $exception) {
             $this->log->error("Response cannot be decoded from json\nException: {$exception->getMessage()}");
+
             return null;
         }
     }
diff --git a/src/Board/PaginatedResult.php b/src/Board/PaginatedResult.php
index c3339aab84f0c3a24e3fa273a0078f2ccd57544f..62f62f4001e99ddab0cd7ddf2b58805b136000a6 100644
--- a/src/Board/PaginatedResult.php
+++ b/src/Board/PaginatedResult.php
@@ -3,7 +3,7 @@
 namespace JiraRestApi\Board;
 
 /**
- * Paginated Result object for BoardService
+ * Paginated Result object for BoardService.
  */
 class PaginatedResult
 {
diff --git a/src/Configuration/ArrayConfiguration.php b/src/Configuration/ArrayConfiguration.php
index df0e6000e7662822bf4b200dba81286eb6874380..267568ba7aea2613a3aa9c0ec5c10a30bc4036c8 100644
--- a/src/Configuration/ArrayConfiguration.php
+++ b/src/Configuration/ArrayConfiguration.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * Created by PhpStorm.
  * User: keanor
diff --git a/src/Configuration/ConfigurationInterface.php b/src/Configuration/ConfigurationInterface.php
index e3c41999cb7861ca40bfd9d4c9ebd746954310a8..0975de0c2d816156a6d23f62d4cc0f5c5dec3c61 100644
--- a/src/Configuration/ConfigurationInterface.php
+++ b/src/Configuration/ConfigurationInterface.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * Created by PhpStorm.
  * User: keanor
diff --git a/src/Epic/EpicService.php b/src/Epic/EpicService.php
index 6213cca0aed301fe403027acb0a51e35e93a7bf6..5b9df95e34d38a4026d2905fb6a777a001d69424 100644
--- a/src/Epic/EpicService.php
+++ b/src/Epic/EpicService.php
@@ -11,7 +11,7 @@ class EpicService extends \JiraRestApi\JiraClient
     private $uri = '/epic';
     private $version = '1.0';
 
-    public function __construct(ConfigurationInterface $configuration = null, LoggerInterface $logger = null, $path = './')
+    public function __construct(?ConfigurationInterface $configuration = null, ?LoggerInterface $logger = null, $path = './')
     {
         parent::__construct($configuration, $logger, $path);
         $this->setAPIUri('/rest/agile/'.$this->version);
diff --git a/src/Issue/AgileIssueService.php b/src/Issue/AgileIssueService.php
index 50ef551100cb60b1f40a0bd215301044236087f9..85bdfcd1782c86e6232d7cb0fe945faee1c6b16e 100644
--- a/src/Issue/AgileIssueService.php
+++ b/src/Issue/AgileIssueService.php
@@ -11,7 +11,7 @@ class AgileIssueService extends \JiraRestApi\JiraClient
 
     private $agileVersion = '1.0';
 
-    public function __construct(ConfigurationInterface $configuration = null, LoggerInterface $logger = null, $path = './')
+    public function __construct(?ConfigurationInterface $configuration = null, ?LoggerInterface $logger = null, $path = './')
     {
         parent::__construct($configuration, $logger, $path);
         $this->setAPIUri('/rest/agile/'.$this->agileVersion);
diff --git a/src/Issue/IssueSearchResult.php b/src/Issue/IssueSearchResult.php
index 3c0cb70ca7298d016b7137b7054d239c04cab422..27b3e9bbfe9a01f1e790612bdd6a65922cf9361f 100644
--- a/src/Issue/IssueSearchResult.php
+++ b/src/Issue/IssueSearchResult.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * Created by PhpStorm.
  * User: keanor
diff --git a/src/Issue/TimeTracking.php b/src/Issue/TimeTracking.php
index cc9ec80684338d7885874401a8d19d21ff2475c9..bf338da8942d515442343431f1a31b2acacb9434 100644
--- a/src/Issue/TimeTracking.php
+++ b/src/Issue/TimeTracking.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * Created by PhpStorm.
  * User: keanor
diff --git a/src/JiraClient.php b/src/JiraClient.php
index 348fb4bc7b51ac746d9ceb2bff44e9f85b2718bb..6c9c55852c5c68ce39e796d621960be4a9f1f34a 100644
--- a/src/JiraClient.php
+++ b/src/JiraClient.php
@@ -59,7 +59,7 @@ class JiraClient
      *
      * @throws JiraException
      */
-    public function __construct(ConfigurationInterface $configuration = null, LoggerInterface $logger = null, string $path = './')
+    public function __construct(?ConfigurationInterface $configuration = null, ?LoggerInterface $logger = null, string $path = './')
     {
         if ($configuration === null) {
             if (!file_exists($path.'.env')) {
@@ -188,7 +188,7 @@ class JiraClient
      *
      * @return string|bool
      */
-    public function exec(string $context, array|string $post_data = null, string $custom_request = null, string $cookieFile = null): string|bool
+    public function exec(string $context, array|string|null $post_data = null, ?string $custom_request = null, ?string $cookieFile = null): string|bool
     {
         $url = $this->createUrlByContext($context);
 
@@ -441,7 +441,7 @@ class JiraClient
     /**
      * Add authorize to curl request.
      */
-    protected function authorization(\CurlHandle $ch, array &$curl_http_headers, string $cookieFile = null): void
+    protected function authorization(\CurlHandle $ch, array &$curl_http_headers, ?string $cookieFile = null): void
     {
         // use cookie
         if ($this->getConfiguration()->isCookieAuthorizationEnabled()) {
@@ -516,7 +516,7 @@ class JiraClient
     /**
      * download and save into outDir.
      */
-    public function download(string $url, string $outDir, string $file, string $cookieFile = null): mixed
+    public function download(string $url, string $outDir, string $file, ?string $cookieFile = null): mixed
     {
         $curl_http_header = [
             'Accept: */*',
diff --git a/src/JiraException.php b/src/JiraException.php
index db14260d663bc5d7d76b95b67a7685e7353496a7..d838a725b2e083f2eefdc881326faef98b09c843 100644
--- a/src/JiraException.php
+++ b/src/JiraException.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * Created by PhpStorm.
  * User: keanor
@@ -23,7 +24,7 @@ class JiraException extends \Exception
     /**
      * Create a new Jira exception instance.
      */
-    public function __construct(?string $message = null, int $code = 0, \Throwable $previous = null, string $response = null)
+    public function __construct(?string $message = null, int $code = 0, ?\Throwable $previous = null, ?string $response = null)
     {
         parent::__construct($message, $code, $previous);
 
diff --git a/src/RapidCharts/ScopeChangeBurnDownChartService.php b/src/RapidCharts/ScopeChangeBurnDownChartService.php
index 3d065269c35514527a608308eccdc1905ea63a82..63409e76f2b3c781bf77c4e5364ba2c08685c2fa 100644
--- a/src/RapidCharts/ScopeChangeBurnDownChartService.php
+++ b/src/RapidCharts/ScopeChangeBurnDownChartService.php
@@ -12,7 +12,7 @@ class ScopeChangeBurnDownChartService extends \JiraRestApi\JiraClient
 
     private $uri = '/rapid/charts/scopechangeburndownchart';
 
-    public function __construct(ConfigurationInterface $configuration = null, LoggerInterface $logger = null, $path = './')
+    public function __construct(?ConfigurationInterface $configuration = null, ?LoggerInterface $logger = null, $path = './')
     {
         parent::__construct($configuration, $logger, $path);
         $this->setupAPIUri();
diff --git a/src/Request/RequestService.php b/src/Request/RequestService.php
index 0db86d6e2453afe4589b594ad0ddbc5242883a11..47b65019e4a80441052e1ead54dcf92f486ef7f1 100644
--- a/src/Request/RequestService.php
+++ b/src/Request/RequestService.php
@@ -23,7 +23,7 @@ class RequestService extends \JiraRestApi\JiraClient
      * @throws JiraException
      * @throws \Exception
      */
-    public function __construct(ConfigurationInterface $configuration = null, LoggerInterface $logger = null, $path = './')
+    public function __construct(?ConfigurationInterface $configuration = null, ?LoggerInterface $logger = null, $path = './')
     {
         parent::__construct($configuration, $logger, $path);
         $this->setupAPIUri();
diff --git a/src/ServiceDesk/Request/RequestService.php b/src/ServiceDesk/Request/RequestService.php
index 33cafcfd9d10504f7bb9b0b5a19a43b4ce284b29..ddae9f175bfded8ea4bcac128f7ab61aab0dc48c 100644
--- a/src/ServiceDesk/Request/RequestService.php
+++ b/src/ServiceDesk/Request/RequestService.php
@@ -65,7 +65,7 @@ class RequestService
      *
      * @see https://docs.atlassian.com/jira-servicedesk/REST/3.6.2/#servicedeskapi/request-getCustomerRequestByIdOrKey
      */
-    public function get(string $issueId, array $expandParameters = [], Request $request = null): Request
+    public function get(string $issueId, array $expandParameters = [], ?Request $request = null): Request
     {
         $request = ($request) ?: new Request();
 
@@ -88,7 +88,7 @@ class RequestService
      *
      * @see https://docs.atlassian.com/jira-servicedesk/REST/3.6.2/#servicedeskapi/request-getMyCustomerRequests
      */
-    public function getRequestsByCustomer(Customer $customer, array $searchParameters, int $serviceDeskId = null): array
+    public function getRequestsByCustomer(Customer $customer, array $searchParameters, ?int $serviceDeskId = null): array
     {
         $defaultSearchParameters = [
             'requestOwnership' => 'OWNED_REQUESTS',
diff --git a/src/ServiceDesk/ServiceDeskClient.php b/src/ServiceDesk/ServiceDeskClient.php
index 579dcaabe0668b7f9165e2cff4a765971a880cc3..d8809cfe87226af7732fc0e60be1336e2cfc3aea 100644
--- a/src/ServiceDesk/ServiceDeskClient.php
+++ b/src/ServiceDesk/ServiceDeskClient.php
@@ -12,8 +12,8 @@ use Psr\Log\LoggerInterface;
 class ServiceDeskClient extends JiraClient
 {
     public function __construct(
-        ConfigurationInterface $configuration = null,
-        LoggerInterface $logger = null,
+        ?ConfigurationInterface $configuration = null,
+        ?LoggerInterface $logger = null,
         string $path = './'
     ) {
         parent::__construct($configuration, $logger, $path);
diff --git a/src/Sprint/SprintSearchResult.php b/src/Sprint/SprintSearchResult.php
index 3c36d524bfd0688826f81c3c36bf7e48313ff60f..7d5611debef9651e0f6195d515cc25b22e1ffd64 100644
--- a/src/Sprint/SprintSearchResult.php
+++ b/src/Sprint/SprintSearchResult.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * Created by PhpStorm.
  * User: keanor
diff --git a/src/Sprint/SprintService.php b/src/Sprint/SprintService.php
index a91b7dc0f4388dd1eb8a1a36bb64d4219123604e..c98f8a6e6571d225843f373eeae3a4f46f25b25b 100644
--- a/src/Sprint/SprintService.php
+++ b/src/Sprint/SprintService.php
@@ -14,7 +14,7 @@ class SprintService extends JiraClient
 {
     private $uri = '/sprint';
 
-    public function __construct(ConfigurationInterface $configuration = null, LoggerInterface $logger = null, $path = './')
+    public function __construct(?ConfigurationInterface $configuration = null, ?LoggerInterface $logger = null, $path = './')
     {
         parent::__construct($configuration, $logger, $path);
         $this->setAPIUri('/rest/agile/1.0');