diff --git a/examples/BankSelection.php b/examples/BankSelection.php
index 98da5d2..7b86dfd 100644
--- a/examples/BankSelection.php
+++ b/examples/BankSelection.php
@@ -7,7 +7,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class BankSelectionExample extends PaymentBasicForms
+final class BankSelectionExample extends PaymentBasicForms
 {
     public function __construct()
     {
diff --git a/examples/BankSelectionAPI.php b/examples/BankSelectionAPI.php
index 12da855..41768b6 100644
--- a/examples/BankSelectionAPI.php
+++ b/examples/BankSelectionAPI.php
@@ -7,7 +7,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class BankSelectionAPIExample extends PaymentBasicForms
+final class BankSelectionAPIExample extends PaymentBasicForms
 {
     public function __construct()
     {
diff --git a/examples/BasicPaymentForm.php b/examples/BasicPaymentForm.php
index 3fb2dc5..0e685e2 100644
--- a/examples/BasicPaymentForm.php
+++ b/examples/BasicPaymentForm.php
@@ -7,7 +7,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class TpayBasicExample extends PaymentBasicForms
+final class TpayBasicExample extends PaymentBasicForms
 {
     public function __construct()
     {
diff --git a/examples/BlikTransactionExample.php b/examples/BlikTransactionExample.php
index fee8bc9..44a40fd 100644
--- a/examples/BlikTransactionExample.php
+++ b/examples/BlikTransactionExample.php
@@ -8,7 +8,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class BlikTransactionExample extends PaymentBlik
+final class BlikTransactionExample extends PaymentBlik
 {
     public function __construct()
     {
diff --git a/examples/CardBasic.php b/examples/CardBasic.php
index bf27552..31d0fe5 100644
--- a/examples/CardBasic.php
+++ b/examples/CardBasic.php
@@ -8,7 +8,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class CardBasic extends PaymentCardForms
+final class CardBasic extends PaymentCardForms
 {
     public function __construct()
     {
diff --git a/examples/CardGate.php b/examples/CardGate.php
index 0640aa0..514b843 100644
--- a/examples/CardGate.php
+++ b/examples/CardGate.php
@@ -9,7 +9,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class CardGate extends PaymentCardForms
+final class CardGate extends PaymentCardForms
 {
     public function __construct()
     {
diff --git a/examples/CardGateExtended.php b/examples/CardGateExtended.php
index 3f4d107..397c16c 100644
--- a/examples/CardGateExtended.php
+++ b/examples/CardGateExtended.php
@@ -9,7 +9,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class CardGateExtended extends PaymentCardForms
+final class CardGateExtended extends PaymentCardForms
 {
     const SUPPORTED_CARD_VENDORS = [
         'visa',
@@ -32,7 +32,7 @@ public function init()
     {
         if (isset($_POST['carddata'])) {
             $this->setPaymentParameters();
-            if (isset($_POST['card_vendor']) && in_array($_POST['card_vendor'], static::SUPPORTED_CARD_VENDORS)) {
+            if (isset($_POST['card_vendor']) && in_array($_POST['card_vendor'], self::SUPPORTED_CARD_VENDORS)) {
                 $this->saveUserCardVendor($_POST['card_vendor']);
             }
             // Try to sale with provided card data
diff --git a/examples/CardNotification.php b/examples/CardNotification.php
index e72e71f..c303d28 100644
--- a/examples/CardNotification.php
+++ b/examples/CardNotification.php
@@ -7,7 +7,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class CardNotification extends CardNotificationHandler
+final class CardNotification extends CardNotificationHandler
 {
     public function __construct()
     {
diff --git a/examples/CardPaymentLinkBuilder.php b/examples/CardPaymentLinkBuilder.php
index 130b495..b36078d 100644
--- a/examples/CardPaymentLinkBuilder.php
+++ b/examples/CardPaymentLinkBuilder.php
@@ -8,7 +8,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class CardPaymentLinkBuilder extends PaymentCardForms
+final class CardPaymentLinkBuilder extends PaymentCardForms
 {
     const REQUIRED_FIELDS = [
         'name',
@@ -63,8 +63,8 @@ public function init()
 
     public function showBuilderForm()
     {
-        $data['currencies'] = static::ALLOWED_CURRENCIES;
-        $data['languages'] = static::ALLOWED_LANGUAGES;
+        $data['currencies'] = self::ALLOWED_CURRENCIES;
+        $data['languages'] = self::ALLOWED_LANGUAGES;
         $data['actionPath'] = '';
         echo $this->getCardPaymentLinkBuilderForm($data);
     }
@@ -72,7 +72,7 @@ public function showBuilderForm()
     public function getCardPaymentLink()
     {
         try {
-            foreach (static::REQUIRED_FIELDS as $fieldName) {
+            foreach (self::REQUIRED_FIELDS as $fieldName) {
                 if (!isset($_POST[$fieldName])) {
                     throw new TException(sprintf('Required field %s is missing', $fieldName));
                 }
diff --git a/examples/CardRefundExample.php b/examples/CardRefundExample.php
index 42e9107..5bc326a 100644
--- a/examples/CardRefundExample.php
+++ b/examples/CardRefundExample.php
@@ -7,7 +7,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class CardRefundExample extends CardRefunds
+final class CardRefundExample extends CardRefunds
 {
     public function __construct()
     {
diff --git a/examples/MassPayment.php b/examples/MassPayment.php
index 5db35b0..b5e66e6 100644
--- a/examples/MassPayment.php
+++ b/examples/MassPayment.php
@@ -8,7 +8,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class MassPaymentExample extends MassPayments
+final class MassPaymentExample extends MassPayments
 {
     const TRID = 'TR-C4Y-HJVWYX';
 
@@ -44,7 +44,7 @@ public function transferMassPayment()
          * Masspayment transfer
          */
         $packId = '123123';
-        $transactionId = static::TRID;
+        $transactionId = self::TRID;
         try {
             $result = $this->massPaymentTransfers($packId, $transactionId);
             print_r($result);
diff --git a/examples/RecurrentPayment.php b/examples/RecurrentPayment.php
index 63b6776..8d77e55 100644
--- a/examples/RecurrentPayment.php
+++ b/examples/RecurrentPayment.php
@@ -7,7 +7,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class RecurrentPayment extends PaymentCard
+final class RecurrentPayment extends PaymentCard
 {
     private $transactionId;
 
diff --git a/examples/SmsNotification.php b/examples/SmsNotification.php
index beb3cc3..06e36b5 100644
--- a/examples/SmsNotification.php
+++ b/examples/SmsNotification.php
@@ -7,7 +7,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class SmsNotification extends PaymentSMS
+final class SmsNotification extends PaymentSMS
 {
     public function __construct()
     {
diff --git a/examples/TransactionApiExample.php b/examples/TransactionApiExample.php
index a48690b..c606641 100644
--- a/examples/TransactionApiExample.php
+++ b/examples/TransactionApiExample.php
@@ -8,7 +8,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class TransactionApiExample extends TransactionApi
+final class TransactionApiExample extends TransactionApi
 {
     private $trId;
 
diff --git a/examples/TransactionNotification.php b/examples/TransactionNotification.php
index bb5d274..9966253 100644
--- a/examples/TransactionNotification.php
+++ b/examples/TransactionNotification.php
@@ -7,7 +7,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class TransactionNotification extends BasicNotificationHandler
+final class TransactionNotification extends BasicNotificationHandler
 {
     public function __construct()
     {
diff --git a/examples/TransactionRefund.php b/examples/TransactionRefund.php
index d649eb9..4b9229a 100644
--- a/examples/TransactionRefund.php
+++ b/examples/TransactionRefund.php
@@ -8,7 +8,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class TransactionRefund extends BasicRefunds
+final class TransactionRefund extends BasicRefunds
 {
     const TRID = 'TR-C4Y-HKR3HX';
 
@@ -29,7 +29,7 @@ public function refundAnyTransaction()
         $amount = 100.00;
 
         try {
-            $this->transactionID = static::TRID;
+            $this->transactionID = self::TRID;
             $result = $this->refundAny($amount);
             print_r($result);
         } catch (TException $e) {
@@ -41,7 +41,7 @@ public function refundTransaction()
     {
         // Refund transaction
         try {
-            $this->transactionID = static::TRID;
+            $this->transactionID = self::TRID;
             $result = $this->refund();
             print_r($result);
         } catch (TException $e) {
diff --git a/examples/TransactionRefundStatus.php b/examples/TransactionRefundStatus.php
index 50a8b7e..ee0873c 100644
--- a/examples/TransactionRefundStatus.php
+++ b/examples/TransactionRefundStatus.php
@@ -8,7 +8,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class TransactionRefundStatus extends BasicReports
+final class TransactionRefundStatus extends BasicReports
 {
     const TRID = 'TR-BRA-KGZK0X';
 
@@ -24,7 +24,7 @@ public function __construct()
     public function getTransactionRefundsStatuses()
     {
         try {
-            $this->transactionID = static::TRID;
+            $this->transactionID = self::TRID;
             $result = $this->transactionRefundStatus();
             var_dump($result);
         } catch (TException $e) {
diff --git a/examples/TransactionReportsApi.php b/examples/TransactionReportsApi.php
index a271d9b..1725b16 100644
--- a/examples/TransactionReportsApi.php
+++ b/examples/TransactionReportsApi.php
@@ -8,7 +8,7 @@
 include_once 'config.php';
 include_once 'loader.php';
 
-class TransactionReportsApi extends BasicReports
+final class TransactionReportsApi extends BasicReports
 {
     public function __construct()
     {