diff --git a/.phan/config.php b/.phan/config.php
index e138932..9679218 100644
--- a/.phan/config.php
+++ b/.phan/config.php
@@ -26,6 +26,7 @@
 // use Phan\Config;
 
 return [
+    "minimum_target_php_version" => "7.4",
     // If true, missing properties will be created when
     // they are first seen. If false, we'll report an
     // error message.
@@ -65,7 +66,7 @@ return [
     'directory_list' => [
         // Change this to include the folders you wish to analyze
         // (and the folders of their dependencies)
-        '.'
+        'src/'
         // 'www',
         // To speed up analysis, we recommend going back later and
         // limiting this to only the vendor/ subdirectories your
diff --git a/phpstan.neon b/phpstan.neon
index a1ca077..b5185b7 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -2,7 +2,7 @@
 
 parameters:
 	tmpDir: %currentWorkingDirectory%/tmp/phpstan-codeblocks-amazon-incentives
-	level: 8
+	level: 9
 	paths:
 		- %currentWorkingDirectory%/src
 	excludePaths:
diff --git a/phpunit.xml b/phpunit.xml
index 1132d19..b004c68 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -1,6 +1,6 @@
 <phpunit
     colors="true"
-    verbose="true"
+    verbose="false"
 >
     <!-- Below removes final from classes for mock tests -->
     <extensions>
diff --git a/src/AWS/AWS.php b/src/AWS/AWS.php
index 7689f5f..f6340e8 100644
--- a/src/AWS/AWS.php
+++ b/src/AWS/AWS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace gullevek\AmazonIncentives\AWS;
 
 use gullevek\AmazonIncentives\Client\Client;
@@ -9,6 +11,7 @@ use gullevek\AmazonIncentives\Debug\AmazonDebug;
 use gullevek\AmazonIncentives\Response\CancelResponse;
 use gullevek\AmazonIncentives\Response\CreateBalanceResponse;
 use gullevek\AmazonIncentives\Response\CreateResponse;
+use gullevek\AmazonIncentives\Handle\Json;
 
 class AWS
 {
@@ -72,12 +75,12 @@ class AWS
         $canonical_request = $this->getCanonicalRequest($service_operation, $payload);
         $date_time_string = $this->getTimestamp();
         AmazonDebug::writeLog(['call' => __METHOD__]);
-        $result = json_decode($this->makeRequest(
+        $result = Json::jsonDecode($this->makeRequest(
             $payload,
             $canonical_request,
             $service_operation,
             $date_time_string
-        ), true);
+        ));
         return new CreateResponse($result);
     }
 
@@ -97,12 +100,12 @@ class AWS
         $canonical_request = $this->getCanonicalRequest($service_operation, $payload);
         $date_time_string = $this->getTimestamp();
         AmazonDebug::writeLog(['call' => __METHOD__]);
-        $result = json_decode($this->makeRequest(
+        $result = Json::jsonDecode($this->makeRequest(
             $payload,
             $canonical_request,
             $service_operation,
             $date_time_string
-        ), true);
+        ));
         return new CancelResponse($result);
     }
 
@@ -120,12 +123,12 @@ class AWS
         $canonical_request = $this->getCanonicalRequest($service_operation, $payload);
         $date_time_string = $this->getTimestamp();
         AmazonDebug::writeLog(['call' => __METHOD__]);
-        $result = json_decode($this->makeRequest(
+        $result = Json::jsonDecode($this->makeRequest(
             $payload,
             $canonical_request,
             $service_operation,
             $date_time_string
-        ), true);
+        ));
         return new CreateBalanceResponse($result);
     }
 
@@ -212,7 +215,7 @@ class AWS
      * @param  string       $date_time_string    Ymd\THis\Z encoded timestamp, getTimestamp()
      * @param  string       $service_target      Target service in the agcod string:
      *                                           Value like com.amazonaws.agcod.<sn>.<so>
-     * @return array<mixed>                      Header data as array for curl request
+     * @return array<int,string>                 Header data as array for curl request
      */
     public function buildHeaders(
         string $payload,
diff --git a/src/AmazonIncentives.php b/src/AmazonIncentives.php
index af5005d..848956b 100644
--- a/src/AmazonIncentives.php
+++ b/src/AmazonIncentives.php
@@ -30,12 +30,12 @@ final class AmazonIncentives
      * @param bool|null $debug      Debug flag
      */
     public function __construct(
-        string $key = null,
-        string $secret = null,
-        string $partner = null,
-        string $endpoint = null,
-        string $currency = null,
-        bool $debug = null
+        ?string $key = null,
+        ?string $secret = null,
+        ?string $partner = null,
+        ?string $endpoint = null,
+        ?string $currency = null,
+        ?bool $debug = null
     ) {
         // load AWS settings
         // fail here if settings missing
@@ -65,7 +65,7 @@ final class AmazonIncentives
      *
      * @throws AmazonErrors
      */
-    public function buyGiftCard(float $value, string $creation_request_id = null): Response\CreateResponse
+    public function buyGiftCard(float $value, ?string $creation_request_id = null): Response\CreateResponse
     {
         return ($this->newAWS())->getCode($value, $creation_request_id);
     }
@@ -109,12 +109,12 @@ final class AmazonIncentives
      * @return AmazonIncentives     self class
      */
     public static function make(
-        string $key = null,
-        string $secret = null,
-        string $partner = null,
-        string $endpoint = null,
-        string $currency = null,
-        bool $debug = null
+        ?string $key = null,
+        ?string $secret = null,
+        ?string $partner = null,
+        ?string $endpoint = null,
+        ?string $currency = null,
+        ?bool $debug = null
     ): AmazonIncentives {
         return new static($key, $secret, $partner, $endpoint, $currency, $debug);
     }
diff --git a/src/Client/Client.php b/src/Client/Client.php
index abea497..1fa02b1 100644
--- a/src/Client/Client.php
+++ b/src/Client/Client.php
@@ -1,9 +1,12 @@
 <?php
 
+declare(strict_types=1);
+
 namespace gullevek\AmazonIncentives\Client;
 
 use gullevek\AmazonIncentives\Exceptions\AmazonErrors;
 use gullevek\AmazonIncentives\Debug\AmazonDebug;
+use gullevek\AmazonIncentives\Handle\Json;
 
 class Client implements ClientInterface
 {
@@ -16,7 +19,7 @@ class Client implements ClientInterface
      *
      * @param  string              $url     The URL being requested,
      *                                      including domain and protocol
-     * @param  array<mixed>        $headers Headers to be used in the request
+     * @param  array<int,string>        $headers Headers to be used in the request
      * @param  array<mixed>|string $params  Can be nested for arrays and hashes
      * @return string                       Result as json string
      */
@@ -50,7 +53,12 @@ class Client implements ClientInterface
             $err = curl_errno($handle);
             AmazonDebug::writeLog(['CURL_REQUEST_RESULT' => $result]);
             // extract all the error codes from Amazon
-            $result_ar = json_decode((string)$result, true);
+            // note we do not care about result errors here, if json decode fails, just set to empty
+            try {
+                $result_ar = Json::jsonDecode((string)$result);
+            } catch (AmazonErrors $e) {
+                $result_ar = [];
+            }
             // if message is 'Rate exceeded', set different error
             if (($result_ar['message'] ?? '') == 'Rate exceeded') {
                 $error_status = 'RESEND';
diff --git a/src/Client/ClientInterface.php b/src/Client/ClientInterface.php
index 8cf67c7..c0c1425 100644
--- a/src/Client/ClientInterface.php
+++ b/src/Client/ClientInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace gullevek\AmazonIncentives\Client;
 
 interface ClientInterface
diff --git a/src/Config/Config.php b/src/Config/Config.php
index 0a9265b..161293c 100644
--- a/src/Config/Config.php
+++ b/src/Config/Config.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace gullevek\AmazonIncentives\Config;
 
 class Config implements ConfigInterface
@@ -85,7 +87,8 @@ class Config implements ConfigInterface
             case 'AWS_GIFT_CARD_PARTNER_ID':
             case 'AWS_GIFT_CARD_ENDPOINT':
             case 'AWS_GIFT_CARD_CURRENCY':
-                $return = (string)($_ENV[$key] ?? '');
+                $return = !empty($_ENV[$key]) && is_string($_ENV[$key]) ?
+                    $_ENV[$key] : '';
                 break;
             default:
                 break;
diff --git a/src/Config/ConfigInterface.php b/src/Config/ConfigInterface.php
index 2721988..16707a5 100644
--- a/src/Config/ConfigInterface.php
+++ b/src/Config/ConfigInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace gullevek\AmazonIncentives\Config;
 
 interface ConfigInterface
diff --git a/src/Debug/AmazonDebug.php b/src/Debug/AmazonDebug.php
index bcbde4a..f6c7c7c 100644
--- a/src/Debug/AmazonDebug.php
+++ b/src/Debug/AmazonDebug.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // simple write all into an array that we can poll in the return group
 // to activate AmazonDebug::setDebug(true) must be called once
 
@@ -7,7 +9,7 @@ namespace gullevek\AmazonIncentives\Debug;
 
 class AmazonDebug
 {
-    /** @var array<mixed> Log data array log id -> array of log entries */
+    /** @var array<string,array<array<mixed>>> Log data array log id -> array of log entries */
     private static $log = [];
     /** @var bool debug flag */
     private static $debug = false;
diff --git a/src/Exceptions/AmazonErrors.php b/src/Exceptions/AmazonErrors.php
index b07612e..aa4baec 100644
--- a/src/Exceptions/AmazonErrors.php
+++ b/src/Exceptions/AmazonErrors.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace gullevek\AmazonIncentives\Exceptions;
 
 use RuntimeException;
@@ -52,7 +54,7 @@ final class AmazonErrors extends RuntimeException
     {
         $message_ar = json_decode($message, true);
         // if we have an error, build empty block and only fill message
-        if (json_last_error()) {
+        if (json_last_error() || $message_ar === null || !is_array($message_ar)) {
             $message_ar = [
                 'status' => '',
                 'code' => '',
diff --git a/src/Handle/Json.php b/src/Handle/Json.php
new file mode 100644
index 0000000..c8eea53
--- /dev/null
+++ b/src/Handle/Json.php
@@ -0,0 +1,42 @@
+<?php
+
+/**
+ * Handle json conversions
+*/
+
+declare(strict_types=1);
+
+namespace gullevek\AmazonIncentives\Handle;
+
+use gullevek\AmazonIncentives\Exceptions\AmazonErrors;
+
+class Json
+{
+    /**
+     * decode json string
+     *
+     * @param  string $json
+     * @return array<mixed>
+     * @throws AmazonErrors
+     */
+    public static function jsonDecode(string $json): array
+    {
+        $result = json_decode($json, true);
+        if (
+            ($json_last_error = json_last_error()) ||
+            $result === null ||
+            !is_array($result)
+        ) {
+            throw AmazonErrors::getError(
+                'FAILURE',
+                'J-' . $json_last_error,
+                'jsonDecoreError',
+                'Failed to decode json data',
+                0
+            );
+        }
+        return $result;
+    }
+}
+
+// __END__
diff --git a/src/Response/CancelResponse.php b/src/Response/CancelResponse.php
index effd540..49b3309 100644
--- a/src/Response/CancelResponse.php
+++ b/src/Response/CancelResponse.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace gullevek\AmazonIncentives\Response;
 
 use gullevek\AmazonIncentives\Debug\AmazonDebug;
diff --git a/src/Response/CreateBalanceResponse.php b/src/Response/CreateBalanceResponse.php
index 953981d..4a3baac 100644
--- a/src/Response/CreateBalanceResponse.php
+++ b/src/Response/CreateBalanceResponse.php
@@ -1,13 +1,15 @@
 <?php
 
+declare(strict_types=1);
+
 namespace gullevek\AmazonIncentives\Response;
 
 use gullevek\AmazonIncentives\Debug\AmazonDebug;
 
 class CreateBalanceResponse
 {
-    /** @var string Amazon Gift Card Balance Amount */
-    protected $amount = '';
+    /** @var float Amazon Gift Card Balance Amount */
+    protected $amount = 0;
     /** @var string Amazon Gift Card Balance Currency */
     protected $currency = '';
     /** @var string Amazon Gift Card Balance Status */
@@ -41,9 +43,9 @@ class CreateBalanceResponse
     /**
      * Return the current available funds amount
      *
-     * @return string Funds amount in set currency
+     * @return float Funds amount in set currency
      */
-    public function getAmount(): string
+    public function getAmount(): float
     {
         return $this->amount;
     }
@@ -98,10 +100,18 @@ class CreateBalanceResponse
      */
     public function parseJsonResponse(array $json_response): self
     {
-        if (array_key_exists('amount', $json_response['availableFunds'])) {
-            $this->amount = $json_response['availableFunds']['amount'];
+        if (
+            is_array($json_response['availableFunds']) &&
+            array_key_exists('amount', $json_response['availableFunds']) &&
+            is_numeric($json_response['availableFunds']['amount'])
+        ) {
+            $this->amount = (float)$json_response['availableFunds']['amount'];
         }
-        if (array_key_exists('currencyCode', $json_response['availableFunds'])) {
+        if (
+            is_array($json_response['availableFunds']) &&
+            array_key_exists('currencyCode', $json_response['availableFunds']) &&
+            is_string($json_response['availableFunds']['currencyCode'])
+        ) {
             $this->currency = $json_response['availableFunds']['currencyCode'];
         }
         // SUCCESS, FAILURE, RESEND
diff --git a/src/Response/CreateResponse.php b/src/Response/CreateResponse.php
index f22813e..f85029c 100644
--- a/src/Response/CreateResponse.php
+++ b/src/Response/CreateResponse.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace gullevek\AmazonIncentives\Response;
 
 use gullevek\AmazonIncentives\Debug\AmazonDebug;
diff --git a/test/phpUnit/AmazonIncentivesTest.php b/test/phpUnit/AmazonIncentivesTest.php
index 66ee87f..1e827c2 100644
--- a/test/phpUnit/AmazonIncentivesTest.php
+++ b/test/phpUnit/AmazonIncentivesTest.php
@@ -351,7 +351,7 @@ final class AmazonIncentivesTest extends TestCase
             // numeric number
             $this->assertIsNumeric(
                 $funds->getAmount(),
-                'Assert amoount is numerc'
+                'Assert amoount is numeric'
             );
             // USD, JPY, etc
             $this->assertIsString(