Quick documentation of invoice properties.

invoice_docs.php

    /**
     * Invoice id.
     */
    public $ID  = 0;

    /**
     * The title of the invoice. Usually the invoice number.
     */
    public $title;

    /**
     * The post type - either wpi_quote or wpi_invoice
     */
    public $post_type;

    /**
     * An array of pending changes.
     */
    public $pending;

    /**
     * An array of invoice items.
     */
    public $items = array();

    /**
     * Information on the invoice client.
     */
    public $user_info = array();

    /**
     * Payment information for the invoice.
     */
    public $payment_meta = array();

    /**
     * Whether this invoice exists in the db or not.
     */
    public $new = false;

    /**
     * The invoice number.
     */
    public $number = '';

    /**
     * Whether an actual payment occurred (live) or the transaction
     * happened in a sandbox environment (test). 
     */
    public $mode = 'live';

    /**
     * A unique key for this invoice.
     */
    public $key = '';

    /**
     * The invoice total.
     */
    public $total = 0.00;

    /**
     * The invoice subtotal.
     */
    public $subtotal = 0;

    /**
     * 1 to disable taxes and 0 otherwise.
     */
    public $disable_taxes = 0;

    /**
     * Total tax for this invoice.
     */
    public $tax = 0;

    /**
     * Other fees for the invoice.
     */
    public $fees = array();

    /**
     * Total amount of the fees.
     */
    public $fees_total = 0;

    /**
     * A comma separated array of discount codes.
     */
    public $discounts = '';

    /**
     * Total discount.
     */
    public $discount = 0;

    /**
     * Main discount code.
     */
    public $discount_code = 0;

    /**
     * The date the invoice was created.
     */
    public $date = '';

    /**
     * The date that the invoice will be due.
     */
    public $due_date = '';

    /**
     * The date the invoice was paid for.
     */
    public $completed_date = '';

    /**
     * The invoice status.
     */
    public $status      = 'wpi-pending';

    /**
     * Same as self::$status.
     */
    public $post_status = 'wpi-pending';

    /**
     * The old invoice status (used when transitioning statuses).
     */
    public $old_status = '';

    /**
     * A human readable status name.
     */
    public $status_nicename = '';

    /**
     * The user id of the invoice client.
     */
    public $user_id = 0;

    /**
     * The first name of the invoice client.
     */
    public $first_name = '';

    /**
     * The last name of the invoice client.
     */
    public $last_name = '';

    /**
     * The email address of the invoice client.
     */
    public $email = '';

    /**
     * The phone number of the invoice client.
     */
    public $phone = '';

    /**
     * The street address of the invoice client.
     */
    public $address = '';

    /**
     * The city of the invoice client.
     */
    public $city = '';

    /**
     * The country of the invoice client.
     */
    public $country = '';

    /**
     * The state of the invoice client.
     */
    public $state = '';

    /**
     * The postal code of the invoice client.
     */
    public $zip = '';

    /**
     * The transaction id of the invoice.
     */
    public $transaction_id = '';

    /**
     * The ip address of the invoice client.
     */
    public $ip = '';

    /**
     * The gateway used to pay the invoice.
     */
    public $gateway = '';

    /**
     * The title of the gateway used to pay for the invoice.
     */
    public $gateway_title = '';

    /**
     * The currency of the invoice.
     */
    public $currency = '';

    /**
     * The cart details of the invoice.
     */
    public $cart_details = array();

    /**
     * The company of the client.
     */
    public $company = '';

    /**
     * The vat number of the client.
     */
    public $vat_number = '';

    /**
     * The vat rate used on the invoice.
     */
    public $vat_rate = '';

    /**
     * Whether or not the client confirmed the address
     */
    public $adddress_confirmed = '';
    
    /**
     * The full name of the client.
     */
    public $full_name = '';

    /**
     * The parent invoice id of this invoice.
     */
    public $parent_invoice = 0;