session managing object

[dombey]

I have been searching the web for information about putting the session functions in an object. I have solved some problems but am stymied on others. I have created a session class in which i call the session_save_handeler in the constructor and it hits methods within the class for start, close, write ... which write the session to the database. This all seems to work. The problem is that i am starting the session withen the class and registering the variables using $_SESSION[] - which is writing to the database, however I am getting a cache limiting headers already sent error at the point where i call session_start in the class.
Why?

[jmcneese]

try mine:

<?php
/**
 * Session 
 *
 * The Session class provides methods to store PHP session
 * data in the database
 *
 * @author      Joshua M. McNeese <[e-mail]>
 * @version     $Revision: 1.1.1.1 $
 * @internal    $Id: Session.class.php,v 1.1.1.1 2003/06/12 09:25:29 jmcneese Exp $
 */

class Session extends PEAR
{

// {{{ Variables

/**
 * Id of the session
 *
 * @var integer
 */
var $id;

/**
 * Database object
 *
 * @var object
 */
var $db;

/**
 * Options array
 *
 * @var array
 */
var $options = array("entropy"  =>  20,
                     "ttl"      =>  1600,
                     "dbtable"  =>  "sessions");
// }}}
// {{{ Constructor

/**
 * Constructor
 *
 * @access public
 * @param object $db Previously instantiated PEAR DB object
 * @return void
 */
function Session($db)
{
    $this->PEAR();
    $this->db = $db;

    session_set_save_handler(
       array(& $this, '_open'),
       array(& $this, '_close'),
       array(& $this, '_read'),
       array(& $this, '_write'),
       array(& $this, '_destroy'),
       array(& $this, '_gc')
    );
}

// }}}
// {{{ _open()

/**
 * Open
 *
 * Empty method for compatibility
 *
 * @access private
 * @return void
 */     
function _open()
{

}

// }}}
// {{{ _close()

/**
 * Close
 *
 * Empty method for compatibility
 *
 * @access private
 * @return void
 */     
function _close()
{

}

// }}}
// {{{ _read()

/**
 * Read a session
 *
 * @access private
 * @param integer $id
 * @return string
 */     
function _read($id)
{
    $res = $this->db->getOne("SELECT data FROM " . $this->options['dbtable'] . " WHERE id = " . $this->db->quote($id));

    if (DB::isError($res)) {
        $this->raiseError("Cannot load session data for id". $id);
    }

    return $res;
}

// }}}
// {{{ _destroy()

/**
 * Destroy a session
 *
 * @access private
 * @param integer $id
 * @return void
 */     
function _destroy($id)
{
    $res= $this->db->query("DELETE FROM " . $this->options['dbtable'] . " WHERE id = " . $this->db->quote($id));

    if(DB::isError($result)) {
       $this->raiseError("Cannot delete session for id $id: ". $result->getMessage());
    }
}

// }}}
// {{{ _write()

/**
 * Write to a session
 *
 * @access private
 * @param integer $id
 * @param string $data
 * @return void
 */     
function _write($id,$data)
{
    $count = $this->db->getOne("SELECT COUNT(*) FROM ". $this->options['dbtable'] ." WHERE id = ". $this->db->quote($id));

    if($count == 0) {
        $sql = "INSERT INTO ". $this->options['dbtable'] ." (id,data,date) VALUES (". $this->db->quote($id) .",". $this->db->quote($data) .",NOW())";

        $res = $this->db->query($sql);

        if (DB::isError($res)) {
           $this->raiseError("Cannot create new session: ". $res->getMessage());
        }

    } else {
        $sql = "UPDATE ". $this->options['dbtable'] ." SET data = ". $this->db->quote($data) .", date = NOW() WHERE id = ". $this->db->quote($id);

        $res = $this->db->query($sql);

        if (DB::isError($res)) {
           $this->raiseError("Cannot update session $id: ". $res->getMessage());
        }
    }

    return $res;
}

// }}}
// {{{ _gc()

/**
 * Garbage collection
 *
 * @access private
 * @return void
 */     
function _gc()
{
   $this->db->query("DELETE FROM ". $this->options['dbtable'] ." WHERE date < NOW() - ". $this->options['ttl']);
}

// }}}
// {{{ Destructor

/**
 * Destructor
 *
 * @access private
 * @return void
 */     
function _Session()
{
    if($this->options['entropy'] > rand(0,100)) {
        $this->_gc();
    }
}

// }}}

}

?>

with this db_table:

DROP TABLE IF EXISTS `sessions`;
CREATE TABLE `sessions` (
  `id` varchar(32) NOT NULL default '',
  `data` text NOT NULL,
  `date` timestamp(14) NOT NULL,
  PRIMARY KEY  (`id`)
) TYPE=MyISAM COMMENT='Session data';

[dombey]

thanks for the help, i did not actually switch to your class but it helped me find an error in mine.
Now i have a question about instantiating this class, I have instaniated it and it works and i can register variables to the database, however after that on a script where i try to call up that registered variable i get an insert error because it tries to insert the same session into the database again?
Why?
Do you instantiate your class on every page that sessions are used?
Any help would be appreciated,
thank you

[jmcneese]

yes, i have a config.inc.php file that is required at the beginning of every file in my application, and the Session class is instantiated there.

$sess  = new Session($db);

[dombey]

you have been extremly helpful, may i ask one more thing?
is there a reason that you do not session_start() in your constructor? does it need to be done outside for some reason?
thank you

[jmcneese]

because i use PEAR::Auth and it initializes the session there.