jedstrom/php-decimal

PHP Decimal Type implementation

1.0.1 2015-11-26 17:01 UTC

Requires

• php: >=5.5.0
• ext-bcmath: *

Requires (Dev)

• phpunit/phpunit: ^5.0

BSD-3-Clause

• Jacob Edstrom

README

jedstrom/php-decimal

A PHP Decimal Type implementation

A value object class that utilizes BCMath functions to perform arbitrary precision arithmetic operations.

Usage

Supported Operations

The following operations are currently supported:

1. Addition
2. Subtraction
3. Multiplication
4. Division

Source

$termOne = new Decimal('2', 2);
$termTwo = new Decimal('3', 0);
var_dump($termOne->add($termTwo)->getValue());
var_dump($termOne->subtract($termTwo)->getValue());
var_dump($termOne->multiply($termTwo)->getValue());
var_dump($termOne->divide($termTwo)->getValue());
// refer to Mixed Precision Calculations section
var_dump($termTwo->add($termOne)->getValue());
var_dump($termTwo->subtract($termOne)->getValue());
var_dump($termTwo->multiply($termOne)->getValue());
var_dump($termTwo->divide($termOne)->getValue());

Output

string(4) "5.00"
string(4) "-1.00"
string(4) "6.00"
string(4) "0.66"
string(4) "5"
string(4) "1"
string(4) "6"
string(4) "2"

Automatic Precision Determination

If the precision is not explicitly set, the precision required to represent the value will be automatically calculated.

Source

$decimal = new Decimal('3.14159');
var_dump($decimal->getPrecision());

Output

int(5)

Rounding Methodology

Rounding is performed using the half away from zero method.

Source

$termOne = new Decimal('1');
$termTwo = new Decimal('1.5');
$product = $termOne->multiply($termTwo);
var_dump($product->getValue());

Output

string(1) "2"

Source

$termOne = new Decimal('-1');
$termTwo = new Decimal('1.5');
$product = $termOne->multiply($termTwo);
var_dump($product->getValue());

Output

string(1) "-2"

Precision Truncation

If a precision is explicitly specified and the value specified requires more precision than specified, the value will be rounded to the specified precision.

Source

$decimal = new Decimal('3.14159', 3);
var_dump($decimal->getValue());

Output

string(5) "3.142"

Mixed Precision Calculations

Calculations are performed internally at the maximum precision of either term + 1 and then rounded to the precision of the first term.

So, in the following example:

19.99 x 0.07125

The internal result is:

1.424287

And the output is rounded to the precision of the first term (19.99 => 2) to produce:

1.42

Source

$price   = new Decimal('19.99', 2);
$taxRate = new Decimal('0.07125', 5');
$tax     = $price->multiply($taxRate);
var_dump($tax);

Output

string(4) "1.42"