enumっぽいやつ。

Enum.php

<?php
namespace src;

use InvalidArgumentException;
use ReflectionObject;

abstract class Enum
{
    private $scalar;

    function __construct($value)
    {
        $ref = new ReflectionObject($this);
        $consts = $ref->getConstants();
        if (!in_array($value, $consts, true)) {
            throw new InvalidArgumentException;
        }

        $this->scalar = $value;
    }

    final static function __callStatic($label, $args)
    {
        $class = get_called_class();
        $const = constant("$class::$label");

        return new $class($const);
    }
    final function valueOf()
    {
        return $this->scalar;
    }

    final function __toString()
    {
        return (string)$this->scalar;
    }
}

Getter.php

<?php

namespace src;

class Getter
{

    /**
     * @param names $name
     * @return names
     */
    public function piyo(names $name)
    {
        return $name;
    }

    /**
     * @param names $name
     * @return bool
     */
    public function check(names $name)
    {
        return $name instanceof names;
    }

}   

Names.php

<?php
namespace src;

class Names extends Enum
{
    CONST A = "hoge";
    CONST C = "hige";
}

test.php

<?php
namespace src;

use PHPUnit_Framework_TestCase;

class test extends PHPUnit_Framework_TestCase
{

    /** @test */
    public function test1()
    {
        $name = new Names(Names::A);
        $getter = new Getter();

        $this->assertEquals('hoge', $getter->piyo($name));
    }

    /** @test */
    public function test2()
    {
        $name = new Names(Names::C);
        $getter = new Getter();

        $this->assertTrue($getter->check($name));
    }


}

参考資料はこちら。
http://qiita.com/Hiraku/items/71e385b56dcaa37629fe