php session过期时间设置，纯新手教学

操作方法：首先打开t.php，然后打开t2.php，不停地刷新t2.php，就会不停的输出username的值。而如果5秒之内不刷新t2.php，就会发现，保存的session值为空了

<?php

    function setSessionTime($expire = 0)
    {
      if ($expire == 0) 
      { $expire = ini_get("session.gc_maxlifetime");}
      else
      {ini_set("session.gc_maxlifetime", $expire);}
        
      setcookie(session_name(), session_id(), time() + $expire);
    }

    session_start();
    setSessionTime(5); //必须放置在session_start()之后
    $_SESSION["username"] = "zwcwu";
?>
<h1> has init scession ! click t2.php to show result </h1>

<?php
	 function setSessionTime($expire = 0)
    {
      if ($expire == 0) 
      { $expire = ini_get("session.gc_maxlifetime");}
      else
      {ini_set("session.gc_maxlifetime", $expire);}
        
      setcookie(session_name(), session_id(), time() + $expire);
    }

    session_start();
    if(empty($_SESSION["username"]))
    {
    	echo "session is null, please relogin now, login!!!!";
    }
    else{
    	setSessionTime(5);
    	echo "Your session value is :" . $_SESSION["username"];
    }

?>