IdentityMapper.php

<?php

use ArrayObject;
use OutOfBoundsException;
use SplObjectStorage;

class IdentityMap
{
    /**
     * @var ArrayObject
     */
    protected $idToObject;
    /**
     * @var SplObjectStorage
     */
    protected $objectToId;
    /**
     * Create an identity map to avoid race conditions
     */
    public function __construct()
    {
        $this->objectToId = new SplObjectStorage();
        $this->idToObject = new ArrayObject();
    }

    /**
     * @param integer $id
     * @param mixed   $object
     */
    public function set($id, $object)
    {
        $this->idToObject[$id]     = $object;
        $this->objectToId[$object] = $id;
    }

    /**
     * @param mixed $object
     *
     * @throws OutOfBoundsException
     * @return integer
     */
    public function getId($object)
    {
        if (false === $this->hasObject($object)) {
            throw new OutOfBoundsException();
        }
        return $this->objectToId[$object];
    }

    /**
     * @param integer $id
     *
     * @return boolean
     */
    public function hasId($id)
    {
        return isset($this->idToObject[$id]);
    }

    /**
     * @param mixed $object
     *
     * @return boolean
     */
    public function hasObject($object)
    {
        return isset($this->objectToId[$object]);
    }

    /**
     * @param integer $id
     *
     * @throws OutOfBoundsException
     * @return object
     */
    public function getObject($id)
    {
        if (false === $this->hasId($id)) {
            throw new OutOfBoundsException();
        }
        return $this->idToObject[$id];
    }
}