ENUM値をオブジェクトにしたい。

Status.php

<?php

class Status
{
    private $value;

    private static $instances = array();

    private function __construct($value)
    {
        $this->value = $value;
    }

    private function _getCacheKey($value)
    {
        return sha1('status_'.$value);
    }

    public static function getInstance($value)
    {
        $key = $this->_getCacheKey($value);
        $cached_instance = apc_fetch($key);
        if ($cached_instance) return $cached_instance;

        if (isset($this->instances[$value])) return $this->instances[$value];

        $instance = new Status($value);
        $this->instances[$value] = $instance;
        apc_add($key, $instance);
        return $instance;
    }
}