diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..d7bed9b
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,16 @@
+version: 2
+updates:
+  - package-ecosystem: "composer"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    commit-message:
+      prefix: "deps"
+    allow:
+      - dependency-type: "direct"
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    commit-message:
+      prefix: "deps"
diff --git a/.github/workflows/netlicensing-php-demo.yml b/.github/workflows/netlicensing-php-demo.yml
new file mode 100644
index 0000000..2c386af
--- /dev/null
+++ b/.github/workflows/netlicensing-php-demo.yml
@@ -0,0 +1,57 @@
+name: PHP Client - Demo Test
+
+on:
+  push:
+    branches:
+      - master
+      - feature/**
+  pull_request:
+    branches:
+      - master
+      - feature/**
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-22.04
+    strategy:
+      fail-fast: false
+      matrix:
+        php-version: ['8.2', '8.3', '8.4']
+
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Setup PHP ${{ matrix.php-version }}
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-version }}
+          coverage: none
+          tools: composer:v2
+
+      - name: Validate composer manifests
+        run: composer validate --strict
+
+      - name: Cache Composer packages
+        id: composer-cache
+        uses: actions/cache@v4
+        with:
+          path: vendor
+          key: ${{ runner.os }}-php-${{ matrix.php-version }}-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-php-${{ matrix.php-version }}-
+
+      - name: Install dependencies
+        run: composer install --prefer-dist --no-progress --no-interaction
+
+      - name: Run PHPUnit
+        run: vendor/bin/phpunit --testsuite "Application Test Suite"
+
+      - name: Run demo scenario (latest PHP)
+        if: matrix.php-version == '8.4'
+        run: |
+          cd demo
+          php NetLicensingDemo.php
diff --git a/.github/workflows/netlicensing-php-dependency-test.yml b/.github/workflows/netlicensing-php-dependency-test.yml
new file mode 100644
index 0000000..cf52230
--- /dev/null
+++ b/.github/workflows/netlicensing-php-dependency-test.yml
@@ -0,0 +1,34 @@
+name: PHP Client - Dependency Test
+
+on:
+  schedule:
+    - cron: '0 2 * * *'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  dependency-check:
+    runs-on: ubuntu-22.04
+    strategy:
+      fail-fast: false
+      matrix:
+        php-version: ['8.4']
+
+    steps:
+      - name: Setup PHP ${{ matrix.php-version }}
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-version }}
+          tools: composer:v2
+
+      - name: Bootstrap temporary project
+        run: |
+          composer create-project --no-interaction --prefer-dist composer/semver netlicensing-php-dependency
+
+      - name: Require NetLicensing client
+        working-directory: netlicensing-php-dependency
+        run: |
+          composer require --no-interaction labs64/netlicensingclient-php
+          composer show labs64/netlicensingclient-php
diff --git a/.github/workflows/netlicensing-php-dependency.yml b/.github/workflows/netlicensing-php-dependency.yml
deleted file mode 100644
index d308852..0000000
--- a/.github/workflows/netlicensing-php-dependency.yml
+++ /dev/null
@@ -1,20 +0,0 @@
-name: PHP Client - Dependency Test
-
-on:
-  schedule:
-    - cron: '*/30 * * * *'
-
-jobs:
-  build:
-
-    runs-on: ubuntu-latest
-
-    steps:
-    - name: Init project
-      run: |
-        composer create-project composer/semver netlicensing-php-dependency
-
-    - name: Install dependencies
-      run: |
-        composer require labs64/netlicensingclient-php
-        composer install --prefer-dist --no-progress --no-suggest
diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
deleted file mode 100644
index 86fa270..0000000
--- a/.github/workflows/php.yml
+++ /dev/null
@@ -1,46 +0,0 @@
-name: PHP Composer
-
-on:
-  push:
-    branches: [ "master" ]
-  pull_request:
-    branches: [ "master" ]
-
-permissions:
-  contents: read
-
-jobs:
-  build:
-
-    runs-on: ubuntu-latest
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Setup PHP
-      uses: shivammathur/setup-php@v2
-      with:
-        php-version: '7.4'
-
-    - name: Validate composer.json and composer.lock
-      run: composer validate --strict
-
-    - name: Cache Composer packages
-      id: composer-cache
-      uses: actions/cache@v3
-      with:
-        path: vendor
-        key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
-        restore-keys: |
-          ${{ runner.os }}-php-
-
-    - name: Install dependencies
-      run: composer install --prefer-dist --no-progress
-
-    # Add a test script to composer.json, for instance: "test": "vendor/bin/phpunit"
-    # Docs: https://getcomposer.org/doc/articles/scripts.md
-
-    - name: Run test suite
-      run: |
-        cd ./demo
-        php ./NetLicensingDemo.php
diff --git a/.gitignore b/.gitignore
index 7f8b48f..fbdf153 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,3 +10,4 @@ Thumbs.db
 .buildpath
 .project
 .settings*
+.phpunit.cache
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 411fec1..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,14 +0,0 @@
-language: php
-
-php:
-  - 7.0
-  - 7.1
-
-before_script:
-  - composer update
-  - cd demo
-  - php NetLicensingDemo.php
-  - cd ..
-
-script:		
-  - vendor/bin/phpunit
diff --git a/README.md b/README.md
index 12bd38f..0453e28 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 # [Labs64 NetLicensing](https://netlicensing.io) Client (PHP)
 
-[![Build Status](https://travis-ci.org/Labs64/NetLicensingClient-php.svg?branch=master)](https://travis-ci.org/Labs64/NetLicensingClient-php)
+[![PHP Client - Demo Test](https://github.com/Labs64/NetLicensingClient-php/actions/workflows/netlicensing-php-demo.yml/badge.svg)](https://github.com/Labs64/NetLicensingClient-php/actions/workflows/netlicensing-php-demo.yml)
 [![Latest Stable Version](https://poser.pugx.org/labs64/netlicensingclient-php/v/stable)](https://packagist.org/packages/labs64/netlicensingclient-php)
 [![Total Downloads](https://poser.pugx.org/labs64/netlicensingclient-php/downloads)](https://packagist.org/packages/labs64/netlicensingclient-php)
 [![Apache License 2.0](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://github.com/Labs64/NetLicensingClient-php/blob/master/LICENSE)
@@ -24,7 +24,7 @@ $ composer require labs64/netlicensingclient-php
 ```
 {
     "require": {
-        "labs64/netlicensingclient-php": "^2.5.0"
+        "labs64/netlicensingclient-php": "^2.6.0"
     }
 }
 ```
@@ -46,6 +46,6 @@ Labs64 NetLicensing Client (PHP) is licensed under the Apache License, Version 2
 Visit Labs64 NetLicensing at https://netlicensing.io
 
 [Labs64 NetLicensing]: https://netlicensing.io
-[RESTful API]: http://l64.cc/nl10
+[RESTful API]: https://netlicensing.io/wiki/restful-api
 [GitHub project]: https://github.com/Labs64/NetLicensingClient-php
 [PSR-2 Coding Standard]: https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md
diff --git a/common/Constants.php b/common/Constants.php
index e13f25c..8a88687 100644
--- a/common/Constants.php
+++ b/common/Constants.php
@@ -11,7 +11,7 @@
 
 class Constants
 {
-    const NETLICENSING_VERSION = '2.5.0';
+    const NETLICENSING_VERSION = '2.6.0';
 
     const NUMBER = 'number';
     const CASCADE = 'forceCascade';
diff --git a/composer.json b/composer.json
index 31b89c2..284afaa 100644
--- a/composer.json
+++ b/composer.json
@@ -37,17 +37,17 @@
     "docs": "https://netlicensing.io/wiki/"
   },
   "require": {
-    "php": ">=7.4",
-    "php-curl-class/php-curl-class": "^11.0.0",
+    "php": ">=8.2",
+    "php-curl-class/php-curl-class": "^11.0.0 || ^12.0.0",
     "fr3d/xmldsig": "^3.0",
     "ext-mbstring": "*",
     "ext-json": "*",
     "ext-dom": "*"
   },
   "require-dev": {
-    "phpunit/phpunit": "~6.5.14",
-    "fzaninotto/faker": "^v1.9.2",
-    "wp-cli/php-cli-tools": "^v0.11.11"
+    "phpunit/phpunit": "^10.5",
+    "fakerphp/faker": "^1.23",
+    "wp-cli/php-cli-tools": "^0.12"
   },
   "autoload": {
     "files": [
diff --git a/demo/NetLicensingDemo.php b/demo/NetLicensingDemo.php
index b89f3f4..72121a0 100644
--- a/demo/NetLicensingDemo.php
+++ b/demo/NetLicensingDemo.php
@@ -863,7 +863,7 @@ public function createLicense()
             $license->setStartDate('now');
             $license->setActive(true);
 
-            $this->license = LicenseService::create($this->context, $this->licensee->getNumber(), $this->licenseeTemplate->getNumber(), null, $license);
+            $this->license = LicenseService::create($this->context, $this->licensee->getNumber(), $this->licenseeTemplate->getNumber(), $license);
 
             //output
             $headers = ['Number', 'Name'];
@@ -941,7 +941,7 @@ public function updateLicense()
 
             $this->license->setName($this->faker->sentence(6, true));
 
-            $this->license = LicenseService::update($this->context, $this->license->getNumber(), null, $this->license);
+            $this->license = LicenseService::update($this->context, $this->license->getNumber(), $this->license);
 
             //output
             $headers = ['Number', 'Name'];
@@ -1263,9 +1263,9 @@ private function error($apiMethod, Exception $exception)
         exit();
     }
 
-    private function table(array $headers, array $rows = null)
+    private function table(array $headers, ?array $rows = null)
     {
-        $table = new Table($headers, $rows, null);
+        $table = new Table($headers, $rows ?? []);
 
         $table->display();
     }
diff --git a/entity/BaseEntity.php b/entity/BaseEntity.php
index 07719fb..f654973 100644
--- a/entity/BaseEntity.php
+++ b/entity/BaseEntity.php
@@ -87,7 +87,7 @@ public function __get(string $key)
      * @param mixed $value
      * @return void
      */
-    public function __set(string $key, $value)
+    public function __set(string $key, mixed $value): void
     {
         $this->setProperty($key, $value);
     }
diff --git a/entity/LicenseTransactionJoin.php b/entity/LicenseTransactionJoin.php
index b7b3cb0..cff5ed7 100644
--- a/entity/LicenseTransactionJoin.php
+++ b/entity/LicenseTransactionJoin.php
@@ -14,7 +14,7 @@ class LicenseTransactionJoin
 
     protected ?License $license = null;
 
-    public function __construct(Transaction $transaction = null, License $license = null)
+    public function __construct(?Transaction $transaction = null, ?License $license = null)
     {
         $this->transaction = $transaction;
         $this->license = $license;
diff --git a/entity/traits/Properties.php b/entity/traits/Properties.php
index 5d47953..4b1a6c9 100644
--- a/entity/traits/Properties.php
+++ b/entity/traits/Properties.php
@@ -43,7 +43,7 @@ trait Properties
      * @return mixed
      * @throws Exception
      */
-    public function getProperty(string $property, $default = null)
+    public function getProperty(string $property, mixed $default = null): mixed
     {
         if (!$property) return $default;
 
@@ -76,7 +76,7 @@ public function getProperties(): array
      * @param  mixed $value
      * @return $this
      */
-    public function setProperty(string $property, $value)
+    public function setProperty(string $property, mixed $value): static
     {
         $this->properties[$property] = ($this->hasCast($property)) ? $this->castSetProperty($property, $value) : $value;
         return $this;
@@ -89,7 +89,7 @@ public function setProperty(string $property, $value)
      * @param $value
      * @return $this
      */
-    public function addProperty($property, $value)
+    public function addProperty(string $property, mixed $value): static
     {
         $this->setProperty($property, $value);
         return $this;
@@ -103,7 +103,7 @@ public function addProperty($property, $value)
      * @param  bool $sync
      * @return $this
      */
-    public function setProperties(array $properties, $sync = false)
+    public function setProperties(array $properties, bool $sync = false): static
     {
         $this->properties = [];
 
@@ -129,7 +129,7 @@ public function setProperties(array $properties, $sync = false)
      * @param $property
      * @return $this
      */
-    public function removeProperty($property)
+    public function removeProperty(string $property): static
     {
         unset($this->properties[$property]);
         return $this;
@@ -142,7 +142,7 @@ public function removeProperty($property)
      * @param  mixed $default
      * @return mixed
      */
-    public function getOriginal(string $property = null, $default = null)
+    public function getOriginal(?string $property = null, mixed $default = null): mixed
     {
         if (is_null($property)) return $this->original;
         return $this->original[$property] ?? $default;
@@ -154,7 +154,7 @@ public function getOriginal(string $property = null, $default = null)
      *
      * @return $this
      */
-    public function syncOriginal()
+    public function syncOriginal(): static
     {
         $this->original = $this->properties;
         return $this;
@@ -166,7 +166,7 @@ public function syncOriginal()
      * @param  string $property
      * @return $this
      */
-    public function syncOriginalProperty(string $property)
+    public function syncOriginalProperty(string $property): static
     {
         $this->original[$property] = $this->properties[$property];
         return $this;
@@ -179,7 +179,7 @@ public function syncOriginalProperty(string $property)
      * @param array|string|null $types
      * @return bool
      */
-    public function hasCast(string $property, $types = null): bool
+    public function hasCast(string $property, array|string|null $types = null): bool
     {
         if (array_key_exists($property, $this->casts)) {
             return !$types || in_array($this->getCastType($property), (array)$types, true);
@@ -205,7 +205,7 @@ protected function getCastType(string $property): string
      * @param  array|string|null $attributes
      * @return bool
      */
-    public function isClean($attributes = null): bool
+    public function isClean(array|string|null $attributes = null): bool
     {
         return !$this->isDirty(...func_get_args());
     }
@@ -216,7 +216,7 @@ public function isClean($attributes = null): bool
      * @param  array|string|null $properties
      * @return bool
      */
-    public function isDirty($properties = null): bool
+    public function isDirty(array|string|null $properties = null): bool
     {
         $dirty = $this->getDirty();
 
@@ -291,7 +291,7 @@ protected function originalIsNumericallyEquivalent(string $property): bool
      * @return mixed
      * @throws Exception
      */
-    protected function castGetProperty(string $property, $value)
+    protected function castGetProperty(string $property, mixed $value): mixed
     {
         if (is_null($value)) {
             return null;
@@ -331,7 +331,7 @@ protected function castGetProperty(string $property, $value)
      * @param mixed $value
      * @return mixed
      */
-    protected function castSetProperty(string $property, $value)
+    protected function castSetProperty(string $property, mixed $value): mixed
     {
         if (is_null($value)) {
             return null;
@@ -382,7 +382,7 @@ protected function fromJson(string $value, bool $asObject = false)
      * @param $value
      * @return string
      */
-    protected function asDateTime($value): string
+    protected function asDateTime(mixed $value): string
     {
 
         // If the value is already a DateTime instance, we will just skip the rest of
diff --git a/phpunit.xml b/phpunit.xml
index 8ec950c..be31f49 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -1,12 +1,15 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit backupGlobals="false" backupStaticAttributes="false" bootstrap="vendor/autoload.php" colors="true"
-         convertErrorsToExceptions="true" convertNoticesToExceptions="true" convertWarningsToExceptions="true"
-         processIsolation="false" stopOnFailure="false">
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true"
+         cacheDirectory=".phpunit.cache"
+         beStrictAboutOutputDuringTests="true"
+         failOnRisky="true"
+         failOnWarning="true">
     <testsuites>
         <testsuite name="Application Test Suite">
-            <directory suffix="Test.php">
-                ./tests
-            </directory>
+            <directory suffix="Test.php">./tests</directory>
         </testsuite>
     </testsuites>
 </phpunit>
diff --git a/service/LicenseService.php b/service/LicenseService.php
index afe940b..e8c17e3 100644
--- a/service/LicenseService.php
+++ b/service/LicenseService.php
@@ -29,21 +29,21 @@ class LicenseService
      *  license template that the license is created from
      * @param string $licenseTemplateNumber
      *
+     * non-null properties will be taken for the new object, null properties will either stay null, or will
+     * be set to a default value, depending on property.
+     * @param License $license
+     *
      * For privileged logins specifies transaction for the license creation. For regular logins new
      * transaction always created implicitly, and the operation will be in a separate transaction.
      * Transaction is generated with the provided transactionNumber, or, if transactionNumber is null, with
      * auto-generated number.
      * @param null|string $transactionNumber
      *
-     * non-null properties will be taken for the new object, null properties will either stay null, or will
-     * be set to a default value, depending on property.
-     * @param License $license
-     *
      * @return License|null
      * @throws MalformedArgumentsException
      * @throws RestException
      */
-    public static function create(Context $context, string $licenseeNumber, string $licenseTemplateNumber, string $transactionNumber = null, License $license): ?License
+    public static function create(Context $context, string $licenseeNumber, string $licenseTemplateNumber, License $license, ?string $transactionNumber = null): ?License
     {
         CheckUtils::paramNotEmpty($licenseeNumber, Constants::LICENSEE_NUMBER);
         CheckUtils::paramNotEmpty($licenseTemplateNumber, Constants::LICENSE_TEMPLATE_NUMBER);
@@ -111,7 +111,7 @@ public static function get(Context $context, string $number): ?License
      * @return Page
      * @throws RestException
      */
-    public static function getList(Context $context, $filter = null): Page
+    public static function getList(Context $context, ?string $filter = null): Page
     {
         $queryParams = (!is_null($filter)) ? [Constants::FILTER => $filter] : [];
 
@@ -146,19 +146,19 @@ public static function getList(Context $context, $filter = null): Page
      * license number
      * @param string $number
      *
+     * non-null properties will be updated to the provided values, null properties will stay unchanged.
+     * @param License $license
+     *
      * transaction for the license update. Created implicitly if transactionNumber is null. In this case the
      * operation will be in a separate transaction.
      * @param string|null $transactionNumber
      *
-     * non-null properties will be updated to the provided values, null properties will stay unchanged.
-     * @param License $license
-     *
      * return updated license.
      * @return License|null
      * @throws MalformedArgumentsException
      * @throws RestException
      */
-    public static function update(Context $context, string $number, string $transactionNumber = null, License $license): ?License
+    public static function update(Context $context, string $number, License $license, ?string $transactionNumber = null): ?License
     {
         CheckUtils::paramNotEmpty($number, Constants::NUMBER);
 
diff --git a/service/LicenseTemplateService.php b/service/LicenseTemplateService.php
index 620a11d..3137a60 100644
--- a/service/LicenseTemplateService.php
+++ b/service/LicenseTemplateService.php
@@ -100,7 +100,7 @@ public static function get(Context $context, string $number): ?LicenseTemplate
      * @return Page
      * @throws RestException
      */
-    public static function getList(Context $context, string $filter = null): Page
+    public static function getList(Context $context, ?string $filter = null): Page
     {
         $queryParams = (!is_null($filter)) ? [Constants::FILTER => $filter] : [];
 
diff --git a/service/LicenseeService.php b/service/LicenseeService.php
index c959c6b..d72eb69 100644
--- a/service/LicenseeService.php
+++ b/service/LicenseeService.php
@@ -102,7 +102,7 @@ public static function get(Context $context, string $number): ?Licensee
      * @return Page
      * @throws RestException
      */
-    public static function getList(Context $context, string $filter = null): Page
+    public static function getList(Context $context, ?string $filter = null): Page
     {
         $queryParams = (!is_null($filter)) ? [Constants::FILTER => $filter] : [];
 
diff --git a/service/NetLicensingService.php b/service/NetLicensingService.php
index 004ef63..2252a98 100644
--- a/service/NetLicensingService.php
+++ b/service/NetLicensingService.php
@@ -214,7 +214,7 @@ protected function validateRestUrl($restUrl): bool
      * @param Context $context
      * @throws RestException
      */
-    private function configure(Context $context)
+    private function configure(Context $context): void
     {
         if (!$context->getSecurityMode()) {
             throw new RestException('Security mode must be specified');
diff --git a/service/PaymentMethodService.php b/service/PaymentMethodService.php
index 0c34a64..25abc18 100644
--- a/service/PaymentMethodService.php
+++ b/service/PaymentMethodService.php
@@ -31,7 +31,7 @@ class PaymentMethodService
      * @throws MalformedArgumentsException
      * @throws RestException
      */
-    public static function get(Context $context, $number): ?PaymentMethod
+    public static function get(Context $context, string $number): ?PaymentMethod
     {
         CheckUtils::paramNotEmpty($number, Constants::NUMBER);
 
@@ -62,7 +62,7 @@ public static function get(Context $context, $number): ?PaymentMethod
      * @return Page
      * @throws RestException
      */
-    public static function getList(Context $context, string $filter = null): Page
+    public static function getList(Context $context, ?string $filter = null): Page
     {
         $queryParams = (!is_null($filter)) ? [Constants::FILTER => $filter] : [];
 
diff --git a/service/ProductModuleService.php b/service/ProductModuleService.php
index 15b954e..76e63e4 100644
--- a/service/ProductModuleService.php
+++ b/service/ProductModuleService.php
@@ -100,7 +100,7 @@ public static function get(Context $context, string $number): ?ProductModule
      * @return Page
      * @throws RestException
      */
-    public static function getList(Context $context, string $filter = null): Page
+    public static function getList(Context $context, ?string $filter = null): Page
     {
         $queryParams = (!is_null($filter)) ? [Constants::FILTER => $filter] : [];
 
diff --git a/service/ProductService.php b/service/ProductService.php
index 484227a..d75b52f 100644
--- a/service/ProductService.php
+++ b/service/ProductService.php
@@ -92,7 +92,7 @@ public static function get(Context $context, string $number): ?Product
      * @return Page
      * @throws RestException
      */
-    public static function getList(Context $context, string $filter = null): Page
+    public static function getList(Context $context, ?string $filter = null): Page
     {
         $queryParams = (!is_null($filter)) ? [Constants::FILTER => $filter] : [];
 
diff --git a/service/TokenService.php b/service/TokenService.php
index edd201c..953316b 100644
--- a/service/TokenService.php
+++ b/service/TokenService.php
@@ -91,7 +91,7 @@ public static function get(Context $context, string $number): ?Token
      * @return Page
      * @throws RestException
      */
-    public static function getList(Context $context, string $filter = null): Page
+    public static function getList(Context $context, ?string $filter = null): Page
     {
         $queryParams = (!is_null($filter)) ? [Constants::FILTER => $filter] : [];
 
diff --git a/service/TransactionService.php b/service/TransactionService.php
index f2a1623..280f8a8 100644
--- a/service/TransactionService.php
+++ b/service/TransactionService.php
@@ -69,7 +69,7 @@ public static function create(Context $context, Transaction $transaction): ?Tran
      * @throws MalformedArgumentsException
      * @throws RestException
      */
-    public static function get(Context $context, $number): ?Transaction
+    public static function get(Context $context, string $number): ?Transaction
     {
         CheckUtils::paramNotEmpty($number, Constants::NUMBER);
 
@@ -100,7 +100,7 @@ public static function get(Context $context, $number): ?Transaction
      * @return Page
      * @throws RestException
      */
-    public static function getList(Context $context, string $filter = null): Page
+    public static function getList(Context $context, ?string $filter = null): Page
     {
         $queryParams = (!is_null($filter)) ? [Constants::FILTER => $filter] : [];
 
diff --git a/service/UtilityService.php b/service/UtilityService.php
index 37afbe2..82d12b6 100644
--- a/service/UtilityService.php
+++ b/service/UtilityService.php
@@ -89,7 +89,7 @@ public static function listLicensingModels(Context $context): Page
      * @return Page
      * @throws RestException
      */
-    public static function listCountries(Context $context, string $filter = null): Page
+    public static function listCountries(Context $context, ?string $filter = null): Page
     {
         $queryParams = (!is_null($filter)) ? [Constants::FILTER => $filter] : [];
 
diff --git a/service/ValidationService.php b/service/ValidationService.php
index eda7411..3fe300f 100644
--- a/service/ValidationService.php
+++ b/service/ValidationService.php
@@ -53,7 +53,7 @@ static public function validate(Context $context, string $number, ValidationPara
      * @throws MalformedArgumentsException
      * @throws RestException
      */
-    static public function retrieveValidationFile(Context $context, string $number, ValidationParameters $validationParameters)
+    static public function retrieveValidationFile(Context $context, string $number, ValidationParameters $validationParameters): mixed
     {
         CheckUtils::paramNotEmpty($number, Constants::NUMBER);
 
diff --git a/vo/Context.php b/vo/Context.php
index f3f25c2..77e3957 100644
--- a/vo/Context.php
+++ b/vo/Context.php
@@ -125,7 +125,7 @@ public function getValues(): array
      * @param mixed $value
      * @return $this
      */
-    public function setValue(string $key, $value): Context
+    public function setValue(string $key, mixed $value): Context
     {
         $this->values[$key] = $value;
         return $this;
@@ -179,7 +179,7 @@ public function __get(string $key)
      * @param mixed $value
      * @return void
      */
-    public function __set(string $key, $value)
+    public function __set(string $key, mixed $value): void
     {
         $this->setValue($key, $value);
     }
@@ -190,7 +190,7 @@ public function __set(string $key, $value)
      * @param string $key
      * @return bool
      */
-    public function __isset(string $key)
+    public function __isset(string $key): bool
     {
         return !is_null($this->getValue($key));
     }
@@ -201,7 +201,7 @@ public function __isset(string $key)
      * @param string $key
      * @return void
      */
-    public function __unset(string $key)
+    public function __unset(string $key): void
     {
         unset($this->values[$key]);
     }
diff --git a/vo/Page.php b/vo/Page.php
index d1cf2c8..f726ae9 100644
--- a/vo/Page.php
+++ b/vo/Page.php
@@ -123,7 +123,7 @@ public function hasNext(): bool
      * @param  mixed $offset
      * @return bool
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return array_key_exists($offset, $this->content);
     }
@@ -134,7 +134,7 @@ public function offsetExists($offset): bool
      * @param  mixed $offset
      * @return mixed
      */
-    public function offsetGet($offset)
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->content[$offset];
     }
@@ -146,7 +146,7 @@ public function offsetGet($offset)
      * @param  mixed $value
      * @return void
      */
-    public function offsetSet($offset, $value)
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->content[] = $value;
@@ -161,7 +161,7 @@ public function offsetSet($offset, $value)
      * @param  mixed $offset
      * @return void
      */
-    public function offsetUnset($offset)
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->content[$offset]);
     }
diff --git a/vo/ValidationParameters.php b/vo/ValidationParameters.php
index b9a1192..32772a3 100644
--- a/vo/ValidationParameters.php
+++ b/vo/ValidationParameters.php
@@ -52,7 +52,7 @@ public function getLicenseeProperties(): array
      * @param $value
      * @return $this
      */
-    public function setLicenseeProperty(string $key, $value): ValidationParameters
+    public function setLicenseeProperty(string $key, mixed $value): ValidationParameters
     {
         $this->licenseeProperties[$key] = $value;
 
@@ -65,9 +65,9 @@ public function setLicenseeProperty(string $key, $value): ValidationParameters
      * @param string $key
      * @return mixed
      */
-    public function getLicenseeProperty(string $key)
+    public function getLicenseeProperty(string $key): mixed
     {
-        return $this->licenseeProperties[$key];
+        return $this->licenseeProperties[$key] ?? null;
     }
 
     /**
@@ -87,9 +87,10 @@ public function setLicenseeName(string $licenseeName): ValidationParameters
         return $this;
     }
 
-    public function getLicenseeName()
+    public function getLicenseeName(): ?string
     {
-        return $this->getLicenseeProperty(Constants::LICENSEE_PROP_LICENSEE_NAME);
+        $value = $this->getLicenseeProperty(Constants::LICENSEE_PROP_LICENSEE_NAME);
+        return is_string($value) ? $value : null;
     }
 
     /**
@@ -111,9 +112,10 @@ public function setLicenseeSecret(string $licenseeSecret): ValidationParameters
     /**
      * @deprecated use 'NodeLocked' licensing model instead
      */
-    public function getLicenseeSecret()
+    public function getLicenseeSecret(): ?string
     {
-        return $this->getLicenseeProperty(Constants::LICENSE_PROP_LICENSEE_SECRET);
+        $value = $this->getLicenseeProperty(Constants::LICENSE_PROP_LICENSEE_SECRET);
+        return is_string($value) ? $value : null;
     }
 
     public function getParameters(): array
@@ -121,7 +123,7 @@ public function getParameters(): array
         return $this->parameters;
     }
 
-    public function getProductModuleValidationParameters($productModuleNumber)
+    public function getProductModuleValidationParameters(string $productModuleNumber): array
     {
         if (empty($this->parameters[$productModuleNumber])) {
             $this->parameters[$productModuleNumber] = array();
@@ -129,7 +131,7 @@ public function getProductModuleValidationParameters($productModuleNumber)
         return $this->parameters[$productModuleNumber];
     }
 
-    public function setProductModuleValidationParameters($productModuleNumber, $productModuleParameters)
+    public function setProductModuleValidationParameters(string $productModuleNumber, array $productModuleParameters): void
     {
         if (empty($this->parameters[$productModuleNumber])) {
             $this->parameters[$productModuleNumber] = array();
diff --git a/vo/ValidationResults.php b/vo/ValidationResults.php
index 9300872..ebf1a49 100644
--- a/vo/ValidationResults.php
+++ b/vo/ValidationResults.php
@@ -32,18 +32,18 @@ public function getValidations(): array
         return $this->validators;
     }
 
-    public function getProductModuleValidation($productModuleNumber)
+    public function getProductModuleValidation(string $productModuleNumber): mixed
     {
         return $this->validators[$productModuleNumber] ?? null;
     }
 
-    public function setProductModuleValidation($productModuleNumber, $productModuleValidation): ValidationResults
+    public function setProductModuleValidation(string $productModuleNumber, mixed $productModuleValidation): ValidationResults
     {
         $this->validators[$productModuleNumber] = $productModuleValidation;
         return $this;
     }
 
-    public function __toString()
+    public function __toString(): string
     {
         $data = 'ValidationResult [';