diff --git a/src/CreditCard.php b/src/CreditCard.php
index 1ca4660..232c772 100644
--- a/src/CreditCard.php
+++ b/src/CreditCard.php
@@ -43,7 +43,7 @@ class CreditCard
      *
      * @return void
      */
-    public function __construct(string $number, string $expiry, int $crypt = 7)
+    public function __construct($number = '', $expiry = '', $crypt = 7)
     {
         $this->number = $number;
         $this->expiry = $expiry;
@@ -73,7 +73,7 @@ public function attach(Customer $customer)
      *
      * @return $this
      */
-    public static function create(string $number, string $expiry, int $crypt = 7)
+    public static function create($number = '', $expiry = '', $crypt = 7)
     {
         return new static($number, $expiry, $crypt);
     }
diff --git a/src/Customer.php b/src/Customer.php
index 18a4b8a..dc79617 100644
--- a/src/Customer.php
+++ b/src/Customer.php
@@ -51,10 +51,10 @@ class Customer
      */
     public function __construct(array $params = [])
     {
-        $this->id = $params['id'] ?? null;
-        $this->email = $params['email'] ?? null;
-        $this->phone = $params['phone'] ?? null;
-        $this->note = $params['note'] ?? null;
+        $this->id = isset($params['id']) ? $params['id'] : null;
+        $this->email = isset($params['email']) ? $params['email'] : null;
+        $this->phone = isset($params['phone']) ? $params['phone'] : null;
+        $this->note = isset($params['note']) ? $params['note'] : null;
     }
 
     /**
diff --git a/src/Gateway.php b/src/Gateway.php
index 55c5f91..2d3d3b7 100644
--- a/src/Gateway.php
+++ b/src/Gateway.php
@@ -80,7 +80,7 @@ class Gateway
      *
      * @return void
      */
-    public function __construct(string $id, string $token, string $environment)
+    public function __construct($id = '', $token = '', $environment = '')
     {
         $this->id = $id;
         $this->token = $token;
@@ -96,11 +96,11 @@ public function __construct(string $id, string $token, string $environment)
      *
      * @return \CraigPaul\Moneris\Response
      */
-    public function capture($transaction, string $order = null, $amount = null)
+    public function capture($transaction, $order = null, $amount = null)
     {
         if ($transaction instanceof Transaction) {
             $order = $transaction->order();
-            $amount = $amount ?? $transaction->amount();
+            $amount = !is_null($amount) ? $amount : $transaction->amount();
             $transaction = $transaction->number();
         }
 
@@ -198,11 +198,11 @@ protected function process(Transaction $transaction)
      *
      * @return \CraigPaul\Moneris\Response
      */
-    public function refund($transaction, string $order = null, $amount = null)
+    public function refund($transaction, $order = null, $amount = null)
     {
         if ($transaction instanceof Transaction) {
             $order = $transaction->order();
-            $amount = $amount ?? $transaction->amount();
+            $amount = !is_null($amount) ? $amount : $transaction->amount();
             $transaction = $transaction->number();
         }
 
@@ -262,7 +262,7 @@ public function verify(array $params = [])
      *
      * @return \CraigPaul\Moneris\Response
      */
-    public function void($transaction, string $order = null)
+    public function void($transaction, $order = null)
     {
         if ($transaction instanceof Transaction) {
             $order = $transaction->order();
diff --git a/src/Moneris.php b/src/Moneris.php
index 571248d..a53e7fb 100644
--- a/src/Moneris.php
+++ b/src/Moneris.php
@@ -55,11 +55,11 @@ class Moneris
      *
      * @return void
      */
-    public function __construct(string $id, string $token, array $params = [])
+    public function __construct($id = '', $token = '', array $params = [])
     {
         $this->id = $id;
         $this->token = $token;
-        $this->environment = $params['environment'] ?? self::ENV_LIVE;
+        $this->environment = isset($params['environment']) ? $params['environment'] : self::ENV_LIVE;
         $this->params = $params;
     }
 
@@ -72,7 +72,7 @@ public function __construct(string $id, string $token, array $params = [])
      *
      * @return \CraigPaul\Moneris\Gateway
      */
-    public static function create(string $id, string $token, array $params = [])
+    public static function create($id = '', $token = '', array $params = [])
     {
         $moneris = new static($id, $token, $params);
 
diff --git a/src/Processor.php b/src/Processor.php
index 17b2ce7..1c3808f 100644
--- a/src/Processor.php
+++ b/src/Processor.php
@@ -49,7 +49,7 @@ public function __construct(Client $client)
      *
      * @return array
      */
-    public function config(string $environment)
+    public function config($environment = '')
     {
         if ($environment === Moneris::ENV_LIVE) {
             $this->config['host'] = 'www3.moneris.com';
@@ -101,7 +101,7 @@ protected function error()
      *
      * @return string
      */
-    protected function send(array $config, string $url, string $xml)
+    protected function send(array $config, $url = '', $xml = '')
     {
         $response = $this->client->post($url, [
             'body' => $xml,
diff --git a/src/Receipt.php b/src/Receipt.php
index 0bd6b39..77b7c61 100644
--- a/src/Receipt.php
+++ b/src/Receipt.php
@@ -92,7 +92,7 @@ protected function prepare($data)
      *
      * @return mixed|null
      */
-    public function read(string $value)
+    public function read($value = '')
     {
         if (isset($this->data[$value]) && !is_null($this->data[$value])) {
             return $this->data[$value];
@@ -116,8 +116,8 @@ private function setData(array $data)
             'email' => isset($data['email']) ? $data['email']->__toString() : '',
             'note' => isset($data['note']) ? $data['note']->__toString() : '',
             'crypt' => isset($data['crypt_type']) ? intval($data['crypt_type']) : null,
-            'masked_pan' => $data['masked_pan'] ?? null,
-            'pan' => $data['pan'] ?? null,
+            'masked_pan' => isset($data['masked_pan']) ? $data['masked_pan'] : null,
+            'pan' => isset($data['pan']) ? $data['pan'] : null,
             'expiry_date' => [
                 'month' => isset($data['expdate']) ? substr($data['expdate'], -2, 2) : null,
                 'year' => isset($data['expdate']) ? substr($data['expdate'], 0, 2) : null,
diff --git a/src/Response.php b/src/Response.php
index 5032e56..792458e 100644
--- a/src/Response.php
+++ b/src/Response.php
@@ -192,7 +192,7 @@ public function validate()
             return $this;
         }
 
-        $code = $receipt->read('avs_result') ?? false;
+        $code = !is_null($receipt->read('avs_result')) ? $receipt->read('avs_result') : false;
 
         if ($gateway->avs && $code && $code !== 'null' && !in_array($code, $gateway->avsCodes)) {
             switch ($code) {
@@ -224,7 +224,7 @@ public function validate()
             return $this;
         }
 
-        $code = $receipt->read('cvd_result') ?? null;
+        $code = !is_null($receipt->read('cvd_result')) ? $receipt->read('cvd_result') : null;
 
         if ($gateway->avs && !is_null($code) && $code !== 'null' && !in_array($code{1}, $gateway->cvdCodes)) {
             $this->status = Response::CVD;
diff --git a/src/Transaction.php b/src/Transaction.php
index ba04176..a90a2a8 100644
--- a/src/Transaction.php
+++ b/src/Transaction.php
@@ -203,7 +203,7 @@ public function valid()
         $params = $this->params;
         $errors = [];
 
-        $errors[] = Validator::empty($params) ? 'No parameters provided.' : null;
+        $errors[] = Validator::isEmpty($params) ? 'No parameters provided.' : null;
 
         if (isset($params['type'])) {
             switch ($params['type']) {
diff --git a/src/Validator.php b/src/Validator.php
index d5f8fa6..6c4d9fa 100644
--- a/src/Validator.php
+++ b/src/Validator.php
@@ -9,7 +9,7 @@ class Validator
      *
      * @return bool
      */
-    public static function empty(array $array = [])
+    public static function isEmpty(array $array = [])
     {
         return empty($array);
     }
@@ -20,7 +20,7 @@ public static function empty(array $array = [])
      *
      * @return bool
      */
-    public static function set(array $array, string $key)
+    public static function set(array $array, $key = '')
     {
         return isset($array[$key]);
     }
diff --git a/src/Vault.php b/src/Vault.php
index 317deb9..2602bdc 100644
--- a/src/Vault.php
+++ b/src/Vault.php
@@ -22,7 +22,7 @@ class Vault extends Gateway
      *
      * @return void
      */
-    public function __construct(string $id, string $token, string $environment)
+    public function __construct($id = '', $token = '', $environment = '')
     {
         parent::__construct($id, $token, $environment);
     }
@@ -57,7 +57,7 @@ public function add(CreditCard $card)
      *
      * @return $this
      */
-    public static function create(string $id, string $token, string $environment)
+    public static function create($id = '', $token = '', $environment = '')
     {
         return new static($id, $token, $environment);
     }
@@ -69,7 +69,7 @@ public static function create(string $id, string $token, string $environment)
      *
      * @return \CraigPaul\Moneris\Response
      */
-    public function delete(string $key)
+    public function delete($key = '')
     {
         $params = [
             'type' => 'res_delete',
@@ -104,7 +104,7 @@ public function expiring()
      *
      * @return \CraigPaul\Moneris\Response
      */
-    public function peek(string $key, bool $full = false)
+    public function peek($key = '', $full = false)
     {
         $params = [
             'type' => $full ? 'res_lookup_full' : 'res_lookup_masked',
@@ -163,7 +163,7 @@ public function purchase(array $params = [])
      *
      * @return \CraigPaul\Moneris\Response
      */
-    public function tokenize($transaction, string $order = null)
+    public function tokenize($transaction, $order = null)
     {
         if ($transaction instanceof Transaction) {
             $order = $transaction->order();
@@ -189,7 +189,7 @@ public function tokenize($transaction, string $order = null)
      *
      * @return \CraigPaul\Moneris\Response
      */
-    public function update(string $key, CreditCard $card)
+    public function update($key = '', CreditCard $card)
     {
         $params = [
             'type' => 'res_update_cc',