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Homephp教程php手册使用数据库保存session的方法

php的session默认是以文件方式保存在服务器端,并且在客户端使用cookie保存变量,这就会出现一个问题,当一个用户由于某种安全原因关闭了浏览器的cookie,程序中的session相关操作将无法执行。因此,如果能以数据库保存session数据,将不受客户端设置的限制,并且在性能和扩展性等方面有一个飞跃。程序中使用关键函数是session_set_save_handler,同时要将php.ini里的session.save_handler = files 改为 user。这里我们讨论的环境是linux(freesd)+apache+mysql+php。

数据表结构:[sessions]
CREATE TABLE sessions (  
sesskey char(32) not null,  
expiry int(11) unsigned not null,  
value text not null,  
PRIMARY KEY (sesskey)  
);

程序代码:[session_inc.php]
$SESS_DBHOST = "yourhost"; /* database server hostname */
$SESS_DBNAME = "yourdb"; /* database name */
$SESS_DBUSER = "youruser"; /* database user */
$SESS_DBPASS = "yourpassword"; /* database password */

$SESS_DBH = "";
$SESS_LIFE = get_cfg_var("session.gc_maxlifetime");

function sess_open($save_path, $session_name) {
    global $SESS_DBHOST, $SESS_DBNAME, $SESS_DBUSER, $SESS_DBPASS, $SESS_DBH;

    if (! $SESS_DBH = mysql_pconnect($SESS_DBHOST, $SESS_DBUSER, $SESS_DBPASS)) {
        echo "
  • Can't connect to $SESS_DBHOST as $SESS_DBUSER";
            echo "
  • MySQL Error: " . mysql_error();
            die;
        }

        if (! mysql_select_db($SESS_DBNAME, $SESS_DBH)) {
            echo "
  • Unable to select database $SESS_DBNAME";
            die;
        }

        return true;
    }

    function sess_close() {
        return true;
    }

    function sess_read($key) {
        global $SESS_DBH, $SESS_LIFE;

        $qry = "SELECT value FROM session_tbl WHERE sesskey = '$key' AND expiry > " . time();
        $qid = mysql_query($qry, $SESS_DBH);

        if (list($value) = mysql_fetch_row($qid)) {
            return $value;
        }

        return false;
    }

    function sess_write($key, $val) {
        global $SESS_DBH, $SESS_LIFE;

        $expiry = time() + $SESS_LIFE; //过期时间
        $value = addslashes($val);

        $qry = "INSERT INTO session_tbl VALUES ('$key', $expiry, '$value')";
        $qid = mysql_query($qry, $SESS_DBH);

        if (! $qid) {
            $qry = "UPDATE session_tbl SET expiry = $expiry, value = '$value' WHERE sesskey = '$key' AND expiry > " . time();
            $qid = mysql_query($qry, $SESS_DBH);
        }

        return $qid;
    }

    function sess_destroy($key) {
        global $SESS_DBH;

        $qry = "DELETE FROM session_tbl WHERE sesskey = '$key'";
        $qid = mysql_query($qry, $SESS_DBH);

        return $qid;
    }

    function sess_gc($maxlifetime) {
        global $SESS_DBH;

        $qry = "DELETE FROM session_tbl WHERE expiry     $qid = mysql_query($qry, $SESS_DBH);

        return mysql_affected_rows($SESS_DBH);
    }

    session_set_save_handler(
    "sess_open",
    "sess_close",
    "sess_read",
    "sess_write",
    "sess_destroy",
    "sess_gc");

    session_start();
    ?>

    完成以上步骤后,在程序中使用require("session_inc.php")来代替session_start()即可,其他的session函数还是象以前一样的方法调用。



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