php session自定义处理

session.gc_probability = 1 // 默认是1 ，越大越好
session.gc_divisor = 100 // 默认是100，越小越好
// 默认是一百次请求调用一次gc 。session.gc_probability相当于分子，session.gc_divisor相当于分母。如果想每次都调用gc 两个改成一样就可以了
session.gc_maxlifetime = 30 // session生存时间
<?php
function session_open($session_path, $session_name)
{
    mysql_connect('localhost', 'root', 'root');
    mysql_select_db('demo');
    mysql_query("SET NAMES utf8");
} 
function session_close()
{
    return true;
} 
function session_read($SID)
{
    $query = "SELECT value FROM session where SID= '$SID' AND expiration >" . time();
    $result = mysql_query($query);
    if (mysql_num_rows($result))
    {
        $row = mysql_fetch_assoc($result);
        $value = $row['value'];
        return $value;
    } 
    else
    {
        return false;
    } 
} 
function session_write($SID, $value)
{
    $lifetime = get_cfg_var("session.gc_maxlifetime");
    $expiration = time() + $lifetime;
    $query = "INSERT INTO session VALUES('$SID', '$expiration', '$value')";
    $result = mysql_query($query);

    if (!$result)
    {
        $query = "UPDATE session SET expiration = '$expiration', value = '$value' WHERE SID = '$SID' AND expiration >" . time();
        $result = mysql_query($query);
    } 
} 
function sessionDestroy($SID)
{
    $query = "DELETE FROM session WHERE SID = '$SID'";
    $result = mysql_query($query);
} 
function session_gc()
{
    $query = "DELETE FROM session WHERE expiration <" . time();
    $result = mysql_query($query);
    echo mysql_affected_rows();
} 
session_set_save_handler("session_open", "session_close", "session_read", "session_write", "sessionDestroy", "session_gc");
session_start();
?>