README

This package is mainly concerned with converting between the following three units of measurement:

• API Gravity
• Barrels per Tonne
• Specific Gravity, AKA "Relative Density"

It was developed to be compatible with PHP 8.0 and greater and is intentionally as light-weight as possible, not requiring any external dependencies or relying on any non-standard PHP libraries.

Please note that future versions may require PHP 8.1 and greater due to the built-in support for Enums that it offers. A new Major release of this library will be released if PHP version dependencies change. At the moment, no significant changes are planned that would require this package to require PHP 8.2 or greater.

Installation

composer require tankertrackers/convert

Usage

If you are doing calculations on an oil grade with a specific gravity (relative density) of 0.983, you can create an Gravity object by calling on the appropriate static method on the TankerTrackers\Convert class like so: Convert::gravity(0.983). If you wanted to see the corresponding API value for this Gravity value, you can instead call Convert::gravity(0.983)->toApi().

Converting all three measurements between each other is done in the same way, and all three methods - ->toApi(), ->toBpt(), and ->toGravity() - are available on all three measurements.

>>> TankerTrackers\Convert::api(34.12)->toBpt();
=> TankerTrackers\FluidMeasures\BarrelsPerTonne {#2684
     +value: 7.3613796475321,
   }

>>> TankerTrackers\Convert::bpt(6.59)->toGravity()
=> TankerTrackers\FluidMeasures\Gravity {#2686
     +value: 0.95437149864956,
   }
   
>>> TankerTrackers\Convert::gravity(1.19)->toApi()
=> TankerTrackers\FluidMeasures\ApiGrade {#2689
     +value: 5.897726515101,
   }

// You can also juggle types back and forth as much as you want.
>>> TankerTrackers\Convert::api(30)->toGravity()->toBpt()->toApi()->toBpt()->toGravity()->toApi()
=> TankerTrackers\FluidMeasures\ApiGrade {#2682
     +value: 30.0,
   }

Note that the $value attribute is always returned as a float; even if the value is 1.0 it is not cast to an int.

You can also access the values directly by calling ->apiValue(), ->bptValue() or ->gravityValue(). This gives the same value as converting to that measurement type and accessing the $value attribute:

>>> TankerTrackers\Convert::api(31)->toGravity()->value
=> 0.87076923076923

>>> TankerTrackers\Convert::api(31)->gravityValue()
=> 0.87076923076923

Future Development

Api Grade Categories

In the future, this package may see some additional bells and whistles when it comes to analyzing the values of the various measurements. For example, the ApiGrade class might offer a ->getCategory() method so that something like this is possible:

>>> $api = Convert::bpt(7.12)->toApi()
>>> $api->getCategory()
=> "Medium"

Pre-defined Listings

I might also consider adding a number of well known oil grades via Enum classes so that one can reference values directly, something like:

>>> \TankerTrackers\Common\Grade::ATHABASCA_BITUMEN->getApi()
=> 31.0
>>> \TankerTrackers\Common\Grade::ATHABASCA_BITUMEN->getGravity()
=> 0.87076923076923

Improvements to Value Checking

At the moment, the system trusts that the values you are entering are valid for that category, so it has no reason to suspect anything is weird if you ask it to create a BarrelsPerTonne object with the value of -718. Some sanity checks could be implemented that catch scenarios like this and throw Exceptions when we know something is out of the ordinary.

Copyright / License

This library is released under an MIT License. See the LICENSE file for further details.