README

ABANDONED! This package is discontinued and will not be updated. See moneyphp/money instead.

Amount

Value objects for monetary amounts.

Features

• Immutable value object.
• Using the bcmath extension for arbitrary floating point arithmetic precision.
• Currency support to prevent mixing currencies.
• Out of the box support for ISO 4217 currencies.
• Simple interface for defining new currencies.
• Support for multiple rounding strategies.
• Support for allocating amounts based on ratios.
• Support for the signal string format as used in the swedish direct debit system.

Installation

composer require byrokrat/amount

Usage

use byrokrat\amount\Amount;

$amount = new Amount('100.6');

// outputs 1 (true)
echo $amount->isGreaterThan(new Amount('50'));

// round to 0 decimal digits
$roundedAmount = $amount->roundTo(0);

// outputs 101.00
echo $roundedAmount;

API

Amount defines the following api:

Creating Amounts from other formats

Floating point numbers

Amount contains two convenience methods for working with floating point numbers. createFromNumber can create an Amount object from a floating point number, getFloat can convert an Amount object to a float. These methods should be used with care.

It is important to note that computers internally use the binary floating point format and cannot accurately represent a number like 0.1, 0.2 or 0.3 at all. Using floating point numbers leads to a loss of precision. For example floor((0.1+0.7)*10) will usually return 7 instead of the expected 8, since the internal representation will be something like 7.9999999999999991118....

For this reason floats should never ne used to store monetary data. These methods exists for rare situations when converting to or from native formats is inevitable. Unless you know what you are doing they should NOT be used.

For more information see the php manual or What Every Programmer Should Know About Floating-Point Arithmetic.

Formatted numbers

You can create Amounts from strings formatted with non-standard or locale dependent decimal point and grouping characters using the static method createFromFormat.

use byrokrat\amount\Amount;

$formattedAmount = "2 000:50";

$amount = Amount::createFromFormat($formattedAmount, ":", " ");

echo $amount;  // outputs 2000.50

Signal strings

The signal string format contans no decimal point and negative amounts are signaled using a letter instead of the final digit. Create Amounts from signal strings using the static method createFromSignalString.

Working with currencies

The currency subsystem helps prevent bugs where values in different currencies are mixed (for example added together). Currency objects subclass Amount and works in the same way, with the added feature that they know their defined currency.

use byrokrat\amount\Currency\SEK;
use byrokrat\amount\Currency\EUR;

$sek = new SEK('100');

// throws an exception
$sek->add(new EUR('1'));

use byrokrat\amount\Currency\SEK;

$sek = new SEK('100');

// works as intended, outputs 101.00
echo $sek->add(new SEK('1'));

ISO 4217

A comprehensive set of ISO 4217 currencies are bundled in the byrokrat\amount\Currency namespace.

Please note that the Turkish Lira with the ISO code TRY is represented as _TRY as try is a reserved keyword.

Creating new currencies

Creating new currencies however is straight forward. Simply subclass the Currency class and define getCurrencyCode().

Additionaly you may override getDisplayPrecision(), getInternalPrecision() and getDefaultRounder() to further define your currency's behaviour.

Exchanging

Exchanging currencies is supported using createFromExchange. Note that you must supply the correct exchange rate.

use byrokrat\amount\Currency\SEK;
use byrokrat\amount\Currency\EUR;

// One euro is exchanged into swedish kronas using the exchange rate 9.27198929
// resulting in the value of SEK 9.27198929
echo $sek = SEK::createFromExchange(new EUR('1'), '9.27198929');

Formatting currencies

Currency objects can easily be formatted using php's built in NumberFormatter.

use byrokrat\amount\Currency\EUR;

// Create some amount of euros
$money = new EUR('1234567.89');

// Create a currency formatter with swedish formatting rules
$formatter = new NumberFormatter('sv_SE', NumberFormatter::CURRENCY);

// Format euros according to swedish standards, outputs 1 234 567:89 €
echo $formatter->formatCurrency($money->getFloat(), $money->getCurrencyCode());

Rounding

A number of rounding strategies are supported. To implement your own see the Rounder interface.

namespace byrokrat\amount;
$amount = new Amount('1.5');

// outputs 2
echo $amount->roundTo(0, new Rounder\RoundUp);

// outputs 1
echo $amount->roundTo(0, new Rounder\RoundDown);

// outputs 1
echo $amount->roundTo(0, new Rounder\RoundTowardsZero);

// outputs 2
echo $amount->roundTo(0, new Rounder\RoundAwayFromZero);

// outputs 2
echo $amount->roundTo(0, new Rounder\RoundHalfUp);

// outputs 1
echo $amount->roundTo(0, new Rounder\RoundHalfDown);

// outputs 1
echo $amount->roundTo(0, new Rounder\RoundHalfTowardsZero);

// outputs 2
echo $amount->roundTo(0, new Rounder\RoundHalfAwayFromZero);

// outputs 2
echo $amount->roundTo(0, new Rounder\RoundHalfToEven);

// outputs 1
echo $amount->roundTo(0, new Rounder\RoundHalfToOdd);

For more info on rounding strategies see wikipedia.

Allocating

Allocating is the process of dividing an amount based on ratios in such a way that the smallest unit is not divided (every currency has a smallest unit that is non-dividable) but instead handed to the receiver next in line.

The ratios can be seen as (but does not have to be) percentages. A hundred units can thous be divided to two receivers as

use byrokrat\amount\Amount;
$money = new Amount('100');

list($receiverA, $receiverB) = $money->allocate([30, 70]);

// outputs 30
echo $receiverA;

// outputs 70
echo $receiverB;

The strength of allocating becomes clear when we distribute a value that we are not able to divide evenly. In this case the order of the receivers is significant.

use byrokrat\amount\Amount;

$money = new Amount('0.05');

list($receiverA, $receiverB) = $money->allocate([30, 70]);

// outputs 0.03
echo $receiverA;

// outputs 0.02
echo $receiverB;

list($receiverA, $receiverB) = $money->allocate([70, 30]);

// outputs 0.04
echo $receiverA;

// outputs 0.01
echo $receiverB;

In these examples the undividable unit used is 0.01. This is the default behaviour. Change it either by specifying the $precision parameter or by overriding getDisplayPrecision() in your currency class.