单点登录实现方法

session的共享

1、首先把session_id的值赋值给cookie，保存在客户端。

2、其次把session_id保存在服务器群都能访问的地方，比如数据库、memcache、radis等等之中

3、根据cookie获取session_id，但是二级域名不同，不能跨域访问cookie，所以，要在php.ini中设置一下

  

ini_set('session.cookie_domain', '.a.com');

4、session放在数据库中

CREATE TABLE sessions (
	session_id varchar(32) NOT NULL,
	session_last_access int(10) unsigned,
	session_data text,
	)PRIMARY KEY (session_id)

<?php 
$gb_DBHOSTname    = "127.0.0.1"; 	//主机的名称或是IP地址
$gb_DBname        = "dbname"; 		//数据库名称
$gb_DBuser        = "username"; 	//数据库用户名称
$gb_DBpass        = "pwd"; 			//数据库密码
$gb_COOKIE_DOMAIN = '.a.com';
$SESS_DBH         = "";
$SESS_LIFE = get_cfg_var("session.gc_maxlifetime"); //得到session的最大有效期。
 session_id(); //不使用 GET/POST 变量方式
ini_set('session.use_trans_sid', 0); //设置垃圾回收最大生存时间
ini_set('session.gc_maxlifetime', 13600); //使用 COOKIE 保存 SESSION ID 的方式
ini_set('session.use_cookies', 1);
ini_set('session.cookie_path', '/'); //多主机共享保存 SESSION ID 的 COOKIE
ini_set("session.cookie_domain", $gb_COOKIE_DOMAIN);
//将 session.save_handler 设置为 user，而不是默认的 files session_module_name('user');
function sess_open($save_path, $session_name) {
    global $gb_DBHOSTname, $gb_DBname, $gb_DBuser, $gb_DBpass, $SESS_DBH;
    if (!$SESS_DBH = mysql_pconnect($gb_DBHOSTname, $gb_DBuser, $gb_DBpass)) {
        die('MySQL Error');
    }
    mysql_query("SET character_set_connection=utf8, character_set_results=utf8, character_set_client=binary", $SESS_DBH);
    if (!mysql_select_db($gb_DBname, $SESS_DBH)) {
        die('MySQL Error');
    }
    return true;
}
function sess_close() {
    global $SESS_DBH;
    //$SESS_DBH->Close();
    return true;
}
function sess_read($key) {
    global $SESS_DBH, $SESS_LIFE;
//      var_dump($SESS_DBH);
    $qry = "select session_data from sessions where session_id = '$key' ";
    $qid = mysql_query($qry, $SESS_DBH);
//      var_dump($qid);
    if (list ($value) = mysql_fetch_row($qid)) {
        return $value;
    }
    return false;
}
function sess_write($key, $val) {
    global $SESS_DBH, $SESS_LIFE;
    $session_last_access = time();
    $value = $val;
    $qry = "insert into  sessions values('$key',$session_last_access,'$value')";
    $qid = mysql_query($qry, $SESS_DBH);
    if (!$qid) {
        $qry = "update sessions set session_last_access=$session_last_access, session_data='$value' where session_id='$key' ";
        $qid = mysql_query($qry, $SESS_DBH);
    }
    return $qid;
}
function sess_destroy($key) {
    global $SESS_DBH;
    $qry = "delete from sessions where session_id = '$key'";
    $qid = mysql_query($qry, $SESS_DBH);
    return $qid;
}
function sess_gc($maxlifetime) {
    global $SESS_DBH;
    $old = time() - $maxlifetime;
    $old = mysql_real_escape_string($old);
    $qry = "delete from sessions where session_last_access < " . $old;
    $qid = mysql_query($qry, $SESS_DBH);
    return mysql_affected_rows($SESS_DBH);
}
session_module_name();
session_set_save_handler("sess_open", "sess_close", "sess_read", "sess_write","sess_destroy", "sess_gc");
session_start();
 ?>