php如何修改session的生存时间

＜?php 
$lifeTime = 24 * 3600; 

session_set_cookie_params($lifeTime); 

session_start();

$name=$_SESSION['yuser']; 

?＞

＜?php

session_start(); 

$lifeTime = 24 * 3600; 

setcookie(session_name(), session_id(), time() + $lifeTime, "/"); 

?＞