diff --git a/src/Models/OrderLine.php b/src/Models/OrderLine.php
index 3cdd454..07f907b 100644
--- a/src/Models/OrderLine.php
+++ b/src/Models/OrderLine.php
@@ -4,38 +4,38 @@
 
 class OrderLine
 {
-    const TYPE_PHYSICAL = 'physical';
-    const TYPE_DISCOUNT = 'discount';
-    const TYPE_SHIPPING_FEE = 'shipping_fee';
-    const TYPE_SALES_TAX = 'sales_tax';
-    const TYPE_DIGITAL = 'digital';
-    const TYPE_GIFT_CARD = 'gift_card';
-    const TYPE_STORE_CREDIT = 'store_credit';
-    const TYPE_SURCHARGE = 'surcharge';
+    public const TYPE_PHYSICAL = 'physical';
+    public const TYPE_DISCOUNT = 'discount';
+    public const TYPE_SHIPPING_FEE = 'shipping_fee';
+    public const TYPE_SALES_TAX = 'sales_tax';
+    public const TYPE_DIGITAL = 'digital';
+    public const TYPE_GIFT_CARD = 'gift_card';
+    public const TYPE_STORE_CREDIT = 'store_credit';
+    public const TYPE_SURCHARGE = 'surcharge';
 
-    public string $type;
-    public string $reference;
-    public string $name;
-    public int $quantity;
-    public int $unit_price;
-    public int $tax_rate;
-    public int $total_amount;
-    public int $total_discount_amount;
-    public ?int $total_tax_amount = null;
-    public string $merchant_data;
-    public ?string $product_url = null;
-    public ?string $image_url = null;
+    public $type;
+    public $reference;
+    public $name;
+    public $quantity;
+    public $unit_price;
+    public $tax_rate;
+    public $total_amount;
+    public $total_discount_amount;
+    public $total_tax_amount;
+    public $merchant_data;
+    public $product_url;
+    public $image_url;
 
-    public function __construct(array $data)
+    public function __construct(array $orderLine)
     {
-        foreach ($data as $prop => $value) {
+        foreach ($orderLine as $prop => $value) {
             if (property_exists($this, $prop)) {
                 $this->$prop = $value;
             }
         }
     }
 
-    public function toArray()
+    public function toArray(): array
     {
         return [
             'type'                  => $this->type,
@@ -52,4 +52,4 @@ public function toArray()
             'image_url'             => $this->image_url,
         ];
     }
-}
\ No newline at end of file
+}