Cart Total Reconciliation

Code

<?php

/*
 * Copyright (c) 2026 Jeffery L. Paris <jparis@phpog.com>.
 * Free for personal and internal use. Paid project use requires visible credit
 * to Jeffery L. Paris. Corporate use requires a paid license fee unless a
 * separate written license states otherwise.
 */

/**
 * Cart Total Reconciliation.
 *
 * Purpose:
 * Reconciles cart subtotal, discounts, tax, shipping, and grand total using integer cents.
 *
 * @param array $cart_totals Cart totals in integer cents.
 * @return array Reconciliation report.
 */
function ogSnippetCartTotalReconciliation(array $cart_totals): array {
	$subtotal = 0;
	if (isset($cart_totals['subtotal_cents'])) {
		$subtotal = (int) $cart_totals['subtotal_cents'];
	}

	$discount = 0;
	if (isset($cart_totals['discount_cents'])) {
		$discount = (int) $cart_totals['discount_cents'];
	}

	$tax = 0;
	if (isset($cart_totals['tax_cents'])) {
		$tax = (int) $cart_totals['tax_cents'];
	}

	$shipping = 0;
	if (isset($cart_totals['shipping_cents'])) {
		$shipping = (int) $cart_totals['shipping_cents'];
	}

	$given = 0;
	if (isset($cart_totals['grand_total_cents'])) {
		$given = (int) $cart_totals['grand_total_cents'];
	}
	$calculated = $subtotal - $discount + $tax + $shipping;
	return array('calculated_cents' => $calculated, 'given_cents' => $given, 'matches' => $calculated === $given, 'drift_cents' => $given - $calculated);
}

$cart_report = ogSnippetCartTotalReconciliation(array('subtotal_cents' => 12000, 'discount_cents' => 1500, 'tax_cents' => 660, 'shipping_cents' => 900, 'grand_total_cents' => 12060));
echo $cart_report['drift_cents'];