我们可以使用session_set_save_handler()来注册连接数据的函数。下面是完整的演示代码

<?php
//
// 'sessions' table schema
// create table sessions (
//   session_id char(32) not null,
//   session_data text not null,
//   session_expiration int(11) unsigned not null,
//   primary key (session_id));
//
  
include_once 'DB.php';
  
// Global Variables
$dbh = NULL;
  
function on_session_start ($save_path, $session_name) {
    global $dbh;
    $dbh = DB::connect('mysql://user:secret@localhost/SITE_SESSIONS',
                       true);
  
    if (DB::isError($dbh)) {
        die(sprintf('Error [%d]: %s',
                    $dbh->getCode(), $dbh->getMessage()));
    }
}
  
function on_session_end ()
{
   // Nothing needs to be done in this function
   // since we used persistent connection.
}
  
function on_session_read ($key)
{
    global $dbh;
  
    $stmt = "select session_data from sessions";
    $stmt .= " where session_id = '$key'";
    $stmt .= " and session_expiration > now()";
  
    $sth = $dbh->query($sth);
    $row = $sth->fetchRow(DB_FETCHMODE_ASSOC);
    return $row['session_data'];
}
  
function on_session_write ($key, $val)
{
    global $dbh;
  
    $val = addslashes($val);
  
    $insert_stmt = "insert into sessions values('$key', '$val', now() + 3600)";
    $update_stmt = "update sessions set session_data = '$val', ";
    $update_stmt .= "session_expiration = now() + 3600 ";
    $update_stmt .= "where session_id = '$key'";
  
    // First we try to insert, if that doesn't succeed, it means
    // session is already in the table and we try to update
    if (DB::isError($dbh->query($insert_stmt)))
        $dbh->query($update_stmt);
}
  
function on_session_destroy ($key)
{
    global $dbh;
  
   $stmt = "delete from sessions where session_id = '$key'";
   $dbh->query($stmt);
}
  
function on_session_gc ($max_lifetime)
{
    global $dbh;
  
    // In this example, we don't use $max_lifetime parameter
    // We simply delete all sessions that have expired
    $stmt = "delete from sessions where session_expiration < now()";
    $dbh->query($stmt);
}
  
session_start ();
  
// Register the $counter variable as part
// of the session
session_register ("counter");
  
// Set the save handlers
session_set_save_handler ("on_session_start",   "on_session_end",
                          "on_session_read",    "on_session_write",
                          "on_session_destroy", "on_session_gc");
  
// Let's see what it does
$counter++;
print $counter;
session_destroy();
?>