README

A PHP library for applying fixed, percentage-based, and custom adjustments to a simp/price Price.

Requirements

PHP 8.1 or later
Composer

Installation

composer require simp/adjustment

Usage

Create adjustments and apply them to a Price. Adjustments are applied in order, so percentage adjustments are calculated against the total after earlier adjustments have been applied. Use a negative value for a discount.

<?php

require 'vendor/autoload.php';

use Simp\Adjustment\lib\Adjustment;
use Simp\Adjustment\lib\Adjustments;
use Simp\Price\lib\Price;

$orderTotal = new Price(100.00, 'USD');

$adjustments = new Adjustments(
    new Adjustment('Service fee', 'Order service fee', 5.00),
    new Adjustment(
        'Seasonal discount',
        'Ten percent seasonal discount',
        -10.0,
        Adjustment::TYPE_PERCENTAGE,
    ),
);

$adjustments->applyTo($orderTotal);

printf(
    "Adjusted total: %s %s\n",
    $orderTotal->getCurrency()->getCode(),
    $orderTotal->getAmount(),
);

The adjusted total in this example is 94.5 USD: the fixed fee is added first, then the percentage discount is calculated from the updated total.

Custom adjustments

For custom calculations, pass a callable as the fifth argument. It receives the current total amount and the adjustment value, and must return a finite number to add to the total.

$bulkDiscount = new Adjustment(
    'Bulk discount',
    'Discount orders of at least $120',
    10.00,
    Adjustment::TYPE_CUSTOM,
    static fn (float $currentTotal, float $discount): float => $currentTotal >= 120
        ? -$discount
        : 0.0,
);

See examples/basic-usage.php and examples/custom-adjustment.php for complete examples.

Managing adjustments

Adjustments accepts any number of Adjustment objects. Use add() and remove() to update the collection, all() to retrieve its items, and iterate over it or call count() to inspect it.

Tests

The test suite uses PHPUnit 13 and requires PHP 8.3 or later. Install the development dependencies and run the tests:

composer install
vendor/bin/phpunit tests

License

This library is available under the MIT License.

simp / adjustment

Package info

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