Php Unit Conversion

The php-unit-conversion/php-unit-conversion package provides full PSR-4 compatible unit conversion. Most other packages that are available for unit conversion are using string types to indicate unit types. In this package all unit types are classes.

We still need to add a lot more units and tests to make the package more usefull. If you want to help me with that, please check Contributing!

Basic Usage

use PhpUnitConversion\Unit\Mass;
$milliGram = new Mass\MilliGram(12);
$milliGram->getValue(); // 12
$milliGram->getSymbol(); // 'mg'

/* A format method is available that accepts two parameters:
 * @integer precision
 * @boolean add_symbol
 */
$milliGram->format(3, false); // 12.000

/* Units are set relative to the BASE_UNIT of the unit type
 * e.g. for Mass the base unit is gram's
 */
echo Mass::BASE_UNIT;
// PhpUnitConversion\Unit\Mass\Gram

/* Most units are linear related to the base unit by a fixed factor
 * For these units you can retrieve the factor by calling getFactor,
 * this can return false if no factor has been defined
 */
echo $milliGram->getFactor();
// 0.001

/* The base unit has no factor defined, this is because we use class constants
 * to define factors for SI prefixes and you can't extend/overwrite constants
 */
var_dump((new Mass\Gram(2))->getFactor());
// false

Unit Conversions

use PhpUnitConversion\Unit;
use PhpUnitConversion\Unit\Mass;

/* If you have an instantiated unit, you can convert to a new unit by calling the 
 * static `from` method on the unit you want to convert to 
 */
$grams = new Mass\Gram(21);
echo Mass\PennyWeight::from($grams)->format();
// 13.503 dwt

/* You can also call the `to` method on the unit object and pass the class name of 
 * the unit you want to convert to 
 */
$grams = new Mass\Gram(21);
$milliGram = $massUnit->to(Mass\MilliGram::class);
echo $milliGram->format(0);
// 21000 mg

/* or use an instantiated object, this will overwrite any existing value
 * due to php passing objects by reference there is no need for a left assignment this way 
 */
$grams = new Mass\Gram(21);
$kiloGram = new Mass\KiloGram;
$grams->to($kiloGram);
echo $kiloGram->format();
// 0.021 kg

/* but `to` also returns the object for left assignment
 */
$massUnit = new Mass\Gram(21);
$ounce = $massUnit->to(new Mass\Ounce);
echo $ounce->format();
// 0.741 oz

/* you can convert directly from a string which has a format of '<value><symbol>' 
 * by calling the static `from` method on the unit class
 */
$milliGrams = Unit::from('21 mg');
var_dump($milliGrams instanceof Mass\MilliGram::class)
// true

/* but if you already know which type of unit to expect, you can also call 
 * `from` directly on the unit type class. This could prevent errors when multiple units
 * exists with the same symbol
 */
$milliGrams = Mass::from('21 mg');
var_dump($milliGrams instanceof Mass\MilliGram::class)
// true

Find the nearest unit type

If you have a value and want to automatically convert it to the unit type which value is closest to 1, you can use the static nearest method. The nearest method should only be called on a Unit Type class.

use PhpUnitConversion\Unit\Mass;
$value = rand(0, 1E13);
$unit = Mass::nearest($value);
echo $unit->format();
// 3.471 long cwt

If you only want units from a specific measurement system, you can pass a System class name as second parameter

use PhpUnitConversion\System;
use PhpUnitConversion\Unit\Mass;

$gram = Mass\Gram(850);

/* Only Units from the Metric system */
$unit = Mass::nearest($value, System\Metric::class);
echo $unit->format();   
// 8.500 hg

/* Only Units from the USC / Imperial system */
$unit = Mass::nearest($value, System\USC::class);
echo $unit->format();   
// 1.874 lb

Storing values with their type

If you want to store values in e.g. a database, you often have to store two things: the value itself and the unit type. As all our Units have a TYPE constant defined, we can use this to add the type information to the value before storing it in the database. To retrieve this unit value you can invoke the class instance itself.

use PhpUnitConversion\Unit\Mass;
$kiloGrams = new Mass\KiloGrams(1);
echo $kiloGrams();
// 64001

The returned value is the result of first converting the value to the base value, then a shift left by 6 and add the TYPE constant.

You can use the static from method to convert to a base unit instance again:

use PhpUnitConversion\Unit;
$grams = Unit::from(64001);
echo get_class($grams);
// PhpUnitConversion\Unit\Mass\Gram

$kiloGrams = $grams->to(Unit\Mass\KiloGram::class);
echo $kiloGrams->format();
// 1 kg

Arithmetic Operators

/* You can add units of the same type by calling `add` method with one or more units as arguments
 * add always returns a new instance
 */
$grams = new Mass\Gram(580);
$addGrams = $massUnit->add(new Mass\KiloGram(0.4), new Mass\Gram(11));
echo $addGrams->format(0);
// 991 g

/* You can also substract units of the same type by calling `substract` method with one or more units
 * as arguments. substract always returns a new instance
 */
$grams = new Mass\Gram(580);
$subGrams = $massUnit->substract(new Mass\KiloGram(0.4), new Mass\Gram(11));
echo $subGrams->format(0);
// 169 g

/* When you try to add/substract units of different types an exception is thrown
 */
$grams = new Mass\Gram(580);
$addGrams = $massUnit->add(new Time\Second(60) );
// throws a PhpUnitConversion\Exception\UnsupportedUnitException

Adding custom units

use PhpUnitConversion\Map as UnitMap;

/* You can add custom units by calling the add method on UnitMap.
 * The first argument should be the path to a directory containing UnitTypes files with
 * the corresponding Unit files in a subfolder.
 * The second argument is the namespace that you use in your files
 */
UnitMap::add('YOUR_UNITS_DIR_OR_FILE', 'YOUR_UNITS_NAMESPACE');

/* If you only want add one unit to an existing unit type, add a third argument with the class name
 * of the unit type you want your unit to add to
 */
UnitMap::add('/path/to/TwoTableSpoons.php', '\\MyUnits', PhpUnitConversion\Unit\Volume::class);

Contributing

Please check Contributing for details.

pimlie/php-unit-conversion