<?php

/**

 * Class MyArrayAccess

 * 提供像访问数组一样访问对象的能力的接口

 */

class MyArrayAccess implements ArrayAccess

{

    private $container;

    public function __construct(Array $arr)

    {

        $this->container = $arr;

    }

    // 某键是否存在 返回布尔值

    public function offsetExists($offset)

    {

        var_dump(__METHOD__);

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

    }

    // 获取键对应的值 返回值mixed

    public function offsetGet($offset)

    {

        var_dump(__METHOD__);

        return isset($this->container[$offset]) ? $this->container[$offset] : null;

    }

    // 赋值

    public function offsetSet($offset, $value)

    {

        if (is_null($offset)) {

            $this->container[] = $value;

        } else {

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

        }

        var_dump(__METHOD__);

    }

    // 删除键值

    public function offsetUnset($offset)

    {

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

        var_dump(__METHOD__);

    }

}

运行：

string(27) "MyArrayAccess::offsetExists"

bool(true)

string(24) "MyArrayAccess::offsetGet"

int(2)

string(26) "MyArrayAccess::offsetUnset"

string(27) "MyArrayAccess::offsetExists"

bool(false)

string(24) "MyArrayAccess::offsetSet"

string(24) "MyArrayAccess::offsetGet"

string(7) "A value"

string(24) "MyArrayAccess::offsetGet"

A valuestring(24) "MyArrayAccess::offsetSet"

string(24) "MyArrayAccess::offsetSet"

string(24) "MyArrayAccess::offsetSet"

object(MyArrayAccess)#1 (1) {

  ["container":"MyArrayAccess":private]=>

  array(6) {

    ["one"]=>

    int(1)

    ["three"]=>

    int(3)

    ["two"]=>

    string(7) "A value"

    [0]=>

    string(8) "Append 1"

    [1]=>

    string(8) "Append 2"

    [2]=>

    string(8) "Append 3"

  }

}

<?php

/**

 * 单例
 * 四私一公

 */

trait Singleton

{

    static private $instance;

    private function __construct()

    {

    }

    private function __clone()

    {

    }

    private function __wakeup()

    {

    }

    static public function getInstance()

    {

        if (is_null(static::$instance)) {

            $class = new ReflectionClass(get_called_class());

            static::$instance = $class->newInstanceWithoutConstructor();

            $method = $class->getConstructor();

            $method->setAccessible(true);

            $method->invokeArgs(static::$instance, func_get_args());

        }

        return static::$instance;

    }

}

/**

 * 对象当数组用

 */

class myAccess implements ArrayAccess

{

    use Singleton;

    private $dataSource = [];

    /**

     * 可返回任意类型

     */

    public function offsetGet($offset)

    {

        var_dump(__METHOD__);

        return $this->dataSource[$offset] ?? null;

    }

    /**

     * 无返回值

     */

    public function offsetSet($offset, $value)

    {

        var_dump(__METHOD__);

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

    }

    /**

     * 返回布尔值

     * 如果用empty()检测且返回值为true，则自动调用offsetGet

     */

    public function offsetExists($offset)

    {

        var_dump(__METHOD__);

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

    }

    /**

     * 无返回值

     */

    public function offsetUnset($offset)

    {

        var_dump(__METHOD__);

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

    }

}

// use

echo '<pre>';

$obj = myAccess::getInstance();

$obj['name'] = 'tom';

isset($obj['name']);

empty($obj['name']);

unset($obj['name']);

var_dump($obj);