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。
(本文来源于图老师网站,更多请访问http://m.tulaoshi.com/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]
<?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 "<liCan't connect to $SESS_DBHOST as $SESS_DBUSER";
echo "<liMySQL Error: " . mysql_error();
die;
}
if (! mysql_select_db($SESS_DBNAME, $SESS_DBH)) {
echo "<liUnable 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);
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