yii2 - PHP 中的 new static($user) 有何作用，如何理解

如何理解PHP中的 new static() 的用法
在yii2的使用者登入處理模型 /model/User.php 看到了這一段：

php [            'id' => '100',            'username' => 'admin',            'password' => 'admin',            'authKey' => 'test100key',            'accessToken' => '100-token',        ],        '101' => [            'id' => '101',            'username' => 'demo',            'password' => 'demo',            'authKey' => 'test101key',            'accessToken' => '101-token',        ],    ];    /**     * @inheritdoc     */    public static function findIdentity($id)    {        return isset(self::$users[$id]) ? new static(self::$users[$id]) : null;    }    /**     * @inheritdoc     */    public static function findIdentityByAccessToken($token, $type = null)    {        foreach (self::$users as $user) {            if ($user['accessToken'] === $token) {                return new static($user);            }        }        return null;    }    /**     * Finds user by username     *     * @param  string      $username     * @return static|null     */    public static function findByUsername($username)    {        foreach (self::$users as $user) {            if (strcasecmp($user['username'], $username) === 0) {                return new static($user);            }        }        return null;    }    /**     * @inheritdoc     */    public function getId()    {        return $this->id;    }    /**     * @inheritdoc     */    public function getAuthKey()    {        return $this->authKey;    }    /**     * @inheritdoc     */    public function validateAuthKey($authKey)    {        return $this->authKey === $authKey;    }    /**     * Validates password     *     * @param  string  $password password to validate     * @return boolean if password provided is valid for current user     */    public function validatePassword($password)    {        return $this->password === $password;    }}

return $user ? new static($user) : null，如果 self::$sers[$id] 裡面沒有 User 類定義的這些屬性，返回就會報錯，為什麼會這樣。如何理解

回複內容：

如何理解PHP中的 new static() 的用法
在yii2的使用者登入處理模型/model/User.php 看到了這一段：

php [            'id' => '100',            'username' => 'admin',            'password' => 'admin',            'authKey' => 'test100key',            'accessToken' => '100-token',        ],        '101' => [            'id' => '101',            'username' => 'demo',            'password' => 'demo',            'authKey' => 'test101key',            'accessToken' => '101-token',        ],    ];    /**     * @inheritdoc     */    public static function findIdentity($id)    {        return isset(self::$users[$id]) ? new static(self::$users[$id]) : null;    }    /**     * @inheritdoc     */    public static function findIdentityByAccessToken($token, $type = null)    {        foreach (self::$users as $user) {            if ($user['accessToken'] === $token) {                return new static($user);            }        }        return null;    }    /**     * Finds user by username     *     * @param  string      $username     * @return static|null     */    public static function findByUsername($username)    {        foreach (self::$users as $user) {            if (strcasecmp($user['username'], $username) === 0) {                return new static($user);            }        }        return null;    }    /**     * @inheritdoc     */    public function getId()    {        return $this->id;    }    /**     * @inheritdoc     */    public function getAuthKey()    {        return $this->authKey;    }    /**     * @inheritdoc     */    public function validateAuthKey($authKey)    {        return $this->authKey === $authKey;    }    /**     * Validates password     *     * @param  string  $password password to validate     * @return boolean if password provided is valid for current user     */    public function validatePassword($password)    {        return $this->password === $password;    }}

return $user ? new static($user) : null，如果 self::$sers[$id] 裡面沒有 User 類定義的這些屬性，返回就會報錯，為什麼會這樣。如何理解

http://stackoverflow.com/questions/5197300/new-self-vs-new-static

這裡有說明

new static : 建立入口對象的新對象。
new self : 建立擁有此方法對象的新對象。
new parent : 建立擁有此方法對象父類的新對象。

