trueskill/src/FactorGraphs/KeyedVariable.php

<?php namespace Moserware\Skills\FactorGraphs;

class KeyedVariable extends Variable
{
    private $_key;

    public function __construct(&$key, $name, &$prior)
    {
        parent::__construct($name, $prior);
        $this->_key = &$key;
    }

    public function &getKey()
    {
        $key = &$this->_key;
        return $key;
    }
}