'Invoice for order #:id', 'invoice' => 'INVOICE', 'order_id' => 'Order ID', 'date' => 'Date', 'order_details' => 'Order Details', 'email' => 'Email', 'phone' => 'Phone', 'payment_method' => 'Payment Method', 'billing_address' => 'Billing Address', 'shipping_address' => 'Shipping Address', 'product' => 'Product', 'unit_price' => 'Unit Price', 'quantity' => 'Quantity', 'line_total' => 'Line Total', 'subtotal' => 'Subtotal', 'coupon' => 'Coupon', 'total' => 'Total', ];