php session存数据库

CREATE TABLE `sessions` ( `session_id` varchar(255) NOT NULL, `session_expires` int(11) DEFAULT NULL, `session_data` text, PRIMARY KEY (`session_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8

<!--?php
//error_reporting(0);
class session {
  
   var $lifeTime;
  
   var $dbHandle;
   function open($savePath, $sessName) {
       
       $this--->lifeTime = get_cfg_var("session.gc_maxlifetime");
       
       $dbHandle = mysql_connect("localhost","root","root");
       $dbSel = mysql_select_db("mysession",$dbHandle);
       
       if(!$dbHandle || !$dbSel)
           return false;
       $this->dbHandle = $dbHandle;
       return true;
   }
   function close() {
       $this->gc(ini_get('session.gc_maxlifetime'));
      
       return @mysql_close($this->dbHandle);
   }
   function read($sessID) {
       
       $res = mysql_query("SELECT session_data AS d FROM sessions
                           WHERE session_id = '$sessID'
                           AND session_expires > ".time(),$this->dbHandle);
       
       if($row = mysql_fetch_assoc($res))
           return $row['d'];
       return "";
   }
   function write($sessID,$sessData) {
	   
	
       
       $newExp = time() + $this->lifeTime;
       
       $res = mysql_query("SELECT * FROM sessions
                           WHERE session_id = '$sessID'",$this->dbHandle);
      
	   
       if($res) {
          
		   
           mysql_query("UPDATE sessions SET session_expires = '{$newExp}',session_data = '{$sessData}' WHERE session_id = '{$sessID}'",$this->dbHandle);
				
           
           if(mysql_affected_rows($this->dbHandle))
               return true;
       }
       
       else {
         
           mysql_query("INSERT INTO sessions (
                         session_id,
                         session_expires,
                         session_data)
                         VALUES(
                         '{$sessID}',
						 '{$newExp}',
						 '{$sessData}')",$this->dbHandle);
           
           if(mysql_affected_rows($this->dbHandle))
               return true;
       }
       
       return false;
   }
   function destroy($sessID) {
       
       mysql_query("DELETE FROM sessions WHERE session_id = '$sessID'",$this->dbHandle);
      
       if(mysql_affected_rows($this->dbHandle))
           return true;
       
       return false;
   }
   function gc($sessMaxLifeTime) {
       
       mysql_query("DELETE FROM sessions WHERE session_expires < ".time(),$this->dbHandle);
       
       return mysql_affected_rows($this->dbHandle);
   }
}
#对session进行测试，发现数据库中并没有存入数据只有session_id,和session_expires的数值,其实session_data是存在的只是我们看不到
 $session = new session();
	session_set_save_handler(array(&$session,"open"),
							 array(&$session,"close"),
							 array(&$session,"read"),
							 array(&$session,"write"),
							 array(&$session,"destroy"),
							 array(&$session,"gc"));
			session_start();
			$session->write(session_id(),json_encode(array("name"=>"gxx","pass"=>"123")));	
			echo $session->read(session_id());
?>  
这里居然不支持插图。。