| 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] <?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 "<li>Can't connect to $SESS_DBHOST as $SESS_DBUSER"; echo "<li>MySQL Error: " . mysql_error(); die; } if (! mysql_select_db($SESS_DBNAME, $SESS_DBH)) { echo "<li>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 < " . time(); $qid = mysql_query($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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