class.order.php

<?php

class Order {

    public function __construct() {
      
        // Setup Orders table
        add_action('init', array( $this, 'setupOrderTable' ) );

        // Create an order when a user completes the form
        add_action('init', array( $this, 'createOrder' ) );

        // Update the order to complete when payment is made.
        add_action('init', array( $this, 'completeOrder' ) );
      
    }

    public function createOrder() {
      
    }

    public function completeOrder() {
    	
    }
    
    public function getOrders() {
      
    }
  
    public function setupOrderTable() {
    	
    }
  
}

$order = new Order();