cacti0.87g 使用php5.4出现错误 "Call to undefined function session_unregister()"

在把gentoo系统全面升级之后，php也升级到了5.4,打开cacti有如下报错
cacti0.87g 使用php5.4出现错误的解决方法,错误内容为：PHP message: PHP Fatal error:  Call to undefined function session_unregister() in /var/www/cacti/site/lib/functions.php on line 410,修改functions.php 410行附近内容为：
解决办法：
functions.php原文件410行原内容
/* kill_session_var - kills a session variable using two methods -- session_unregister() and unset() */
function kill_session_var($var_name) {
        /* register_global = off: reset local settings cache so the user sees the new settings */
        session_unregister($var_name);

        /* register_global = on: reset local settings cache so the user sees the new settings */
        unset($_SESSION[$var_name]);
}

修改后的内容，把原文红色部分注释掉
/* kill_session_var - kills a session variable using two methods -- session_unregister() and unset() */
function kill_session_var($var_name) {
        /* register_global = off: reset local settings cache so the user sees the new settings */
        /* session_unregister($var_name); */

        /* register_global = on: reset local settings cache so the user sees the new settings */
        unset($_SESSION[$var_name]);
}