first_name 和last_name 不属于_users 表it是用户元数据。因此，用户对象没有它。所以当你访问该物业时first_name 用户对象有一个PHP魔术方法__get()

/**
 * Magic method for accessing custom fields
 *
 * @since 3.3.0
 * @param string $key
 * @return mixed
 */
public function __get( $key ) {
    if ( \'id\' == $key ) {
        _deprecated_argument( \'WP_User->id\', \'2.1\', __( \'Use <code>WP_User->ID</code> instead.\' ) );
        return $this->ID;
    }

    if ( isset( $this->data->$key ) ) {
        $value = $this->data->$key;
    } else {
        if ( isset( self::$back_compat_keys[ $key ] ) )
            $key = self::$back_compat_keys[ $key ];
        $value = get_user_meta( $this->ID, $key, true );
    }

    if ( $this->filter ) {
        $value = sanitize_user_field( $key, $value, $this->ID, $this->filter );
    }

    return $value;
}