将PHP的session数据存储到数据库中的代码实例

一个开发环境有多个网站，需要使用不同的session，解决方案很多。不过这次也高大上一把，用数据库存，方便以后扩展。

PostgreSQL版
首先是数据库的部分

--drop table php_sessioncreate 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_sessioncreate or replace function del_session(varchar) returns void as $del_session$  delete from php_session where sess_id = $1$del_session$ language sql;--gc_sessioncreate 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;

然后是PHP的部分

<?phpsession_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');?>

然后只要在session_start之前调用这个就可以了

至于SESSION_CONN，那是我定义的一个常量，表示一个指向session数据库的链接而已。

MySQL版
再总结一个针对MySQL的集成更多基础功能的例子：
表结构：

 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;

session信息存储到数据库的类：

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;    }  } }