/**

 * Interface to provide accessing objects as arrays.

 * @link http://php.net/manual/en/class.arrayaccess.php

 */

interface ArrayAccess {

    /**

     * Whether a offset exists

     * @link http://php.net/manual/en/arrayaccess.offsetexists.php

     * @param mixed $offset <p>

     * An offset to check for.

     * </p>

     * @return boolean true on success or false on failure.

     * </p>

     * <p>

     * The return value will be casted to boolean if non-boolean was returned.

     * @since 5.0.0

     */

    public function offsetExists($offset);

    /**

     * Offset to retrieve

     * @link http://php.net/manual/en/arrayaccess.offsetget.php

     * @param mixed $offset <p>

     * The offset to retrieve.

     * </p>

     * @return mixed Can return all value types.

     * @since 5.0.0

     */

    public function offsetGet($offset);

    /**

     * Offset to set

     * @link http://php.net/manual/en/arrayaccess.offsetset.php

     * @param mixed $offset <p>

     * The offset to assign the value to.

     * </p>

     * @param mixed $value <p>

     * The value to set.

     * </p>

     * @return void

     * @since 5.0.0

     */

    public function offsetSet($offset, $value);

    /**

     * Offset to unset

     * @link http://php.net/manual/en/arrayaccess.offsetunset.php

     * @param mixed $offset <p>

     * The offset to unset.

     * </p>

     * @return void

     * @since 5.0.0

     */

    public function offsetUnset($offset);

}

class Container implements ArrayAccess

{

    /**

     * @var array 单例对象索引

     */

    private $instances = [];

    /**

     * @var array 可实例化对象定义索引

     */

    private $definitions = [];

    public function offsetExists($offset)

    {

        return isset($this->definitions[$offset]);

    }

    public function offsetGet($offset)

    {

        if (isset($this->instances[$offset])) {

            return $this->instances[$offset];

        } elseif (isset($this->definitions[$offset])) {

            return $this->make($offset);

        }

        throw new \Exception('未提供对象定义');

    }

    public function offsetSet($offset, $value)

    {

        // ... 省略一些较验判断

        $this->definitions[$offset] = $value;

    }

    public function offsetUnset($offset)

    {

        unset($this->definitions[$offset]);

        unset($this->instances[$offset]);

    }

    private function make($offset)

    {

        $definition = $this->definitions[$offset];

        if ($definition instanceof \Closure) {

            return $this->instances[$offset] = $definition();

        }

        if (is_object($definition)) {

            return $this->instances[$offset] = $definition;

        }

        if (is_array($definition)) {

            $class = $definition['class'];

            $reflection = new \ReflectionClass($class);

            $dependencies = [];

            // ... 省略反射的实现代码

            $object = $reflection->newInstanceArgs($dependencies);

            return $this->instances[$offset] = $object;

        }

        throw new \Exception('对象定义不合法');

    }

}

$container = new Container();

$container['test'] = function () {

  return 'this is a test';

};

var_dump(isset($container['test']));

echo $container['test'];

unset($container['test']);