diff --git a/README.md b/README.md
index 0b064df..c08100c 100644
--- a/README.md
+++ b/README.md
@@ -16,13 +16,17 @@ composer require paysgator/paysgator-php
 
 For most requests, you simply need to provide your API Key.
 
+> **Security:** Never hardcode API keys. Use environment variables.
+> **Error Handling:** All API calls throw exceptions. Wrap requests in try-catch blocks.
+
+
 ```php
 require 'vendor/autoload.php';
 
 use Paysgator\PaysgatorClient;
 
 $client = new PaysgatorClient([
-    'api_key' => 'YOUR_API_KEY',
+    'api_key' => getenv('PAYSGATOR_API_KEY'),
 ]);
 ```
 
diff --git a/composer.json b/composer.json
index 8c0d054..3cce55f 100644
--- a/composer.json
+++ b/composer.json
@@ -1,7 +1,7 @@
 {
     "name": "paysgator/paysgator-php",
     "description": "Paysgator API Client for PHP",
-    "version": "1.0.0",
+    "version": "2.0.0",
     "type": "library",
     "license": "MIT",
     "authors": [
@@ -11,7 +11,7 @@
         }
     ],
     "require": {
-        "php": "^7.4 || ^8.0",
+        "php": "^8.0",
         "guzzlehttp/guzzle": "^7.8"
     },
     "autoload": {
diff --git a/index.php b/index.php
index 970f7d0..d7649dd 100644
--- a/index.php
+++ b/index.php
@@ -8,8 +8,15 @@
     'base_url' => 'https://paysgator.com/api/v1/', // Optional, defaults to production
 ]);
 
-$apiKey="";
-$walletId="";
+$apiKey = getenv('PAYSGATOR_API_KEY') ?: '';
+$walletId = getenv('PAYSGATOR_WALLET_ID') ?: '';
+
+if (empty($apiKey) || empty($walletId)) {
+    die('Error: Missing credentials. Set PAYSGATOR_API_KEY and PAYSGATOR_WALLET_ID environment variables.');
+}
+
+
+try {
 
 // Authenticate to get a new token (automatically sets it on the client)
 $response = $client->auth()->authenticate($apiKey, $walletId);
@@ -31,4 +38,9 @@
 ]);
 
 print_r($directCharge);
+} catch (\Exception $e) {
+    error_log('Payment error: ' . $e->getMessage());
+    echo 'An error occurred: ' . $e->getMessage();
+}
+
 
diff --git a/src/PaysgatorClient.php b/src/PaysgatorClient.php
index ae8682b..cbca606 100644
--- a/src/PaysgatorClient.php
+++ b/src/PaysgatorClient.php
@@ -3,7 +3,6 @@
 namespace Paysgator;
 
 use GuzzleHttp\Client;
-use GuzzleHttp\Exception\GuzzleException;
 use Paysgator\Resources\Payments;
 use Paysgator\Resources\Subscriptions;
 use Paysgator\Resources\Transactions;
@@ -37,7 +36,11 @@ public function __construct(array $config = [])
 
     public function setApiKey($key)
     {
+        if ($this->apiKey === $key) {
+            return;
+        }
         $this->apiKey = $key;
+
         $config = $this->client->getConfig();
         $config['headers']['X-Api-Key'] = $key;
         $this->client = new Client($config);
diff --git a/src/Resources/Payments.php b/src/Resources/Payments.php
index 38ddcbb..3901f98 100644
--- a/src/Resources/Payments.php
+++ b/src/Resources/Payments.php
@@ -3,6 +3,7 @@
 namespace Paysgator\Resources;
 
 use Paysgator\PaysgatorClient;
+use Exception;
 
 class Payments
 {
@@ -21,11 +22,18 @@ public function __construct(PaysgatorClient $client)
      */
     public function create(array $data)
     {
-        $response = $this->client->getHttpClient()->post('payment/create', [
-            'json' => $data,
-        ]);
-
-        return json_decode($response->getBody()->getContents(), true);
+        if (empty($data)) {
+            throw new Exception('Payment data cannot be empty');
+        }
+        try {
+            $response = $this->client->getHttpClient()->post('payment/create', [
+                'json' => $data,
+            ]);
+
+            return json_decode($response->getBody()->getContents(), true);
+        } catch (Exception $e) {
+            throw new Exception('Failed to create payment: ' . $e->getMessage(), $e->getCode(), $e);
+        }
     }
 
     /**
@@ -36,10 +44,17 @@ public function create(array $data)
      */
     public function confirm(array $data)
     {
-        $response = $this->client->getHttpClient()->post('payment/confirm', [
-            'json' => $data,
-        ]);
-
-        return json_decode($response->getBody()->getContents(), true);
+        if (empty($data)) {
+            throw new Exception('Payment data cannot be empty');
+        }
+        try {
+            $response = $this->client->getHttpClient()->post('payment/confirm', [
+                'json' => $data,
+            ]);
+
+            return json_decode($response->getBody()->getContents(), true);
+        } catch (Exception $e) {
+            throw new Exception('Failed to confirm payment: ' . $e->getMessage(), $e->getCode(), $e);
+        }
     }
 }
diff --git a/src/Resources/Subscriptions.php b/src/Resources/Subscriptions.php
index 0ffd103..999e438 100644
--- a/src/Resources/Subscriptions.php
+++ b/src/Resources/Subscriptions.php
@@ -22,10 +22,25 @@ public function __construct(PaysgatorClient $client)
      */
     public function update($id, $action)
     {
-        $response = $this->client->getHttpClient()->patch("subscriptions/{$id}", [
-            'json' => ['action' => $action],
-        ]);
+        if (empty($id) || !is_string($id)) {
+            throw new \InvalidArgumentException('Subscription ID is required.');
+        }
+        if (empty($action) || !is_string($action)) {
+            throw new \InvalidArgumentException('Action is required.');
+        }
 
-        return json_decode($response->getBody()->getContents(), true);
+        try {
+            $response = $this->client->getHttpClient()->patch("subscriptions/{$id}", [
+                'json' => ['action' => $action],
+            ]);
+
+            if ($response->getStatusCode() >= 400) {
+                throw new \RuntimeException('API request failed: ' . $response->getReasonPhrase());
+            }
+
+            return json_decode($response->getBody()->getContents(), true);
+        } catch (\Exception $e) {
+            throw new \RuntimeException('Failed to update subscription: ' . $e->getMessage(), 0, $e);
+        }
     }
 }
diff --git a/src/Resources/Transactions.php b/src/Resources/Transactions.php
index 3455b47..0c96f44 100644
--- a/src/Resources/Transactions.php
+++ b/src/Resources/Transactions.php
@@ -3,6 +3,10 @@
 namespace Paysgator\Resources;
 
 use Paysgator\PaysgatorClient;
+use Exception;
+use InvalidArgumentException;
+use RuntimeException;
+
 
 class Transactions
 {
@@ -21,7 +25,15 @@ public function __construct(PaysgatorClient $client)
      */
     public function get($id)
     {
-        $response = $this->client->getHttpClient()->get("transactions/{$id}");
+        if (empty($id) || !is_string($id)) {
+            throw new InvalidArgumentException('Transaction ID must be a non-empty string');
+        }
+
+        try {
+            $response = $this->client->getHttpClient()->get("transactions/{$id}");
+        } catch (Exception $e) {
+            throw new RuntimeException('Failed to fetch transaction: ' . $e->getMessage(), 0, $e);
+        }
 
         return json_decode($response->getBody()->getContents(), true);
     }
diff --git a/src/Resources/Wallet.php b/src/Resources/Wallet.php
index f51805b..2a938ac 100644
--- a/src/Resources/Wallet.php
+++ b/src/Resources/Wallet.php
@@ -3,6 +3,8 @@
 namespace Paysgator\Resources;
 
 use Paysgator\PaysgatorClient;
+use GuzzleHttp\Exception\RequestException;
+
 
 class Wallet
 {
@@ -18,10 +20,19 @@ public function __construct(PaysgatorClient $client)
      *
      * @return array
      */
-    public function getBalance()
+    public function getBalance(): array
     {
-        $response = $this->client->getHttpClient()->get('wallet/balance');
+        try {
+            $response = $this->client->getHttpClient()->get('wallet/balance');
+            $data = json_decode($response->getBody()->getContents(), true);
+
+            if (json_last_error() !== JSON_ERROR_NONE) {
+                throw new \RuntimeException('Invalid JSON response from API');
+            }
 
-        return json_decode($response->getBody()->getContents(), true);
+            return $data;
+        } catch (RequestException $e) {
+            throw new \RuntimeException('API Request failed: ' . $e->getMessage(), $e->getCode(), $e);
+        }
     }
 }