--drop table php_session
create unlogged table php_session
(
 sess_id varchar(32) primary key,
 modify_time timestamp with time zone not null,
 sess_data varchar(3000) default ''
);

create index concurrently idx_php_session_modify_time on php_session(modify_time);

--set_session(id, data)
create or replace function set_session(varchar, varchar) returns void as $set_session$
 with upsert as (
  update php_session
  set modify_time = current_timestamp, sess_data = $2
  where sess_id = $1
  returning 1
 )
 insert into php_session (sess_id, modify_time, sess_data)
 select $1, current_timestamp, $2
 where not exists (
  select 1 from upsert
 );
$set_session$ language sql;

--get_session(id)
create or replace function get_session(varchar) returns varchar as $get_session$
 select sess_data from php_session where sess_id = $1
$get_session$ language sql;

--del_session
create or replace function del_session(varchar) returns void as $del_session$
 delete from php_session where sess_id = $1
$del_session$ language sql;

--gc_session
create or replace function gc_session() returns void as $del_session$
 delete from php_session where modify_time < current_timestamp - interval '30 days'
$del_session$ language sql;

<?php

session_set_save_handler(
 function ($savePath, $sessionName) {//open
  return true;
 },
 function () {//close
  return true;
 },
 function ($id) {//read
  $sql = "select get_session($1)";
  $stmt = pg_query_params(SESSION_CONN, $sql, array($id));
  $result = pg_fetch_row($stmt);
  
  return $result[0];
 },
 function ($id, $data) {//write
  $sql = "select set_session($1, $2)";
  pg_query_params(SESSION_CONN, $sql, array($id, $data));
  return true;
 },
 function ($id) {//destroy
  $sql = "select del_session($1)";
  pg_query_params(SESSION_CONN, $sql, array($id, $data));
  return true;
 },
 function ($maxlifetime) {//gc
  //php needn't control the global session gc 
  return true;
 }
);

register_shutdown_function('session_write_close');

?>

 CREATE TABLE IF NOT EXISTS `sessioninfo` (
 `sid` varchar(255) NOT NULL,
 `value` text NOT NULL,
 `expiration` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
 PRIMARY KEY (`sid`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

class MySessionHandler implements SessionHandlerInterface {
 
 /**
 * @access private
 * @var object 数据库连接
 */
 private $_dbLink;
 /**
 * @access private
 * @var string 保存session的表名
 */
 Private $_sessionTable;
 /**
 * @access private
 * @var string session名
 */
 private $_sessionName;
 /**
 * @const 过期时间
 */
 const SESSION_EXPIRE = 10;
 
 public function __construct($dbLink, $sessionTable) {
  if(!is_object($dbLink)) {
   return false;
  }
  $this->_dbLink = $dbLink;
  $this->_sessionTable = $sessionTable;
 }
 
 /**
 * 打开
 * @access public
 * @param string $session_save_path 保存session的路径
 * @param string $session_name session名
 * @return integer
 */
 public function open($session_save_path, $session_name) {
  $this->_sessionName = $session_name;
  return 0;
 }
 
 /**
 * 关闭
 * @access public
 * @return integer
 */
 public function close() {
  return 0;
 }
 
 /**
 * 关闭session
 * @access public
 * @param string $session_id session ID
 * @return string
 */
 public function read($session_id) {
  $query = "SELECT value FROM {$this->_sessionTable} WHERE sid = {$session_id} AND UNIX_TIMESTAMP(expiration) + " . self::SESSION_EXPIRE . " > UNIX_TIMESTAMP(NOW())";
  $result = $this->_dbLink->query($query);
  if(!isset($value) || empty($value)) {
   $value = "";
   return $value;
  }
  $this->_dbLink->query("UPDATE {$this->_sessionTable} SET expiration = CURRENT_TIMESTAMP() WHERE sid = {$session_id}");
  $value = $result->fetch_array();
  $result->free();
  return $value['value'];
 }
 
 /**
 * 写入session
 * @access public
 * @param string $session_id session ID
 * @param string $session_data session data
 * @return integer
 */
 public function write($session_id, $session_data) {
  $query = "SELECT value FROM {$this->_sessionTable} WHERE sid = '{$session_id}' AND UNIX_TIMESTAMP(expiration) + " . self::SESSION_EXPIRE . " > UNIX_TIMESTAMP(NOW())";
  $result = $this->_dbLink->query($query);
  $result = $result->fetch_array();
  if(!empty($result)) {
   $result = $this->_dbLink->query("UPDATE {$this->_sessionTable} SET value = {$session_data} WHERE sid = {$session_id}");
  }
  else{
   $result = $this->_dbLink->query("INSERT INTO {$this->_sessionTable} (sid, value) VALUES ('{$session_id}', '{$session_data}')");
  }
  if($result){
   return 0;
  }
  else{
   return 1;
  }  
 }
 
 /**
 * 销魂session
 * @access public
 * @param string $session_id session ID
 * @return integer
 */
 public function destroy($session_id) {
  $result = $this->_dbLink->query("DELETE FROM {$this->_sessionTable} WHERE sid = '{$session_id}'");
  if($result){
   return 0;
  }
  else{
   return 1;
  }
 }
 
 /**
 * 垃圾回收
 * @access public
 * @param string $maxlifetime session 最长生存时间
 * @return integer
 */
 public function gc($maxlifetime) {
  $result = $this->_dbLink->query("DELETE FROM {$this->_sessionTable} WHERE UNIX_TIMESTAMP(expiration) < UNIX_TIMESTAMP(NOW()) - " . self::SESSION_EXPIRE);
  if($result){
   return 0;
  }
  else{
   return 1;
  }
 }
 
}

$dbLink = new mysqli("localhost", "root", "root", "test");
$sessionTable = "sessioninfo";
 
$handler = new MySessionHandler($dbLink, $sessionTable);
session_set_save_handler($handler);
session_start();
$_SESSION['name'] = "test";
echo $_SESSION["name"];
//session_destroy();