Custom CI Session library to detect user_id this file only extend and modified sess_update and sess_write function note: must add "user_id" field to ci_session table

MY_Session

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class MY_Session extends CI_Session {

  public function __construct($params = array())
	{
		parent::__construct($params);
	}

	function sess_write()
	{
		// Are we saving custom data to the DB?  If not, all we do is update the cookie
		if ($this->sess_use_database === FALSE)
		{
			$this->_set_cookie();
			return;
		}

		// set the custom userdata, the session data we will set in a second
		$custom_userdata = $this->userdata;
		$cookie_userdata = array();

		// Before continuing, we need to determine if there is any custom data to deal with.
		// Let's determine this by removing the default indexes to see if there's anything left in the array
		// and set the session data while we're at it
		foreach (array('session_id','ip_address','user_agent','last_activity') as $val)
		{
			unset($custom_userdata[$val]);
			$cookie_userdata[$val] = $this->userdata[$val];
		}

		// Did we find any custom data?  If not, we turn the empty array into a string
		// since there's no reason to serialize and store an empty array in the DB
		if (count($custom_userdata) === 0)
		{
			$custom_userdata = '';
		}
		else
		{
			// Serialize the custom data array so we can store it
			$custom_userdata = $this->_serialize($custom_userdata);
		}

		// Run the update query
		$this->CI->db->where('session_id', $this->userdata['session_id']);
		
		// hack to set user id if already login
		$me = $this->CI->session->userdata('me');
		$me = (isset($me['id']) && $me['id'] != 0) ? $me['id'] : 0;
		
		$this->CI->db->update($this->sess_table_name, array('last_activity' => $this->userdata['last_activity'], 'user_data' => $custom_userdata,'user_id' => $me));

		// Write the cookie.  Notice that we manually pass the cookie data array to the
		// _set_cookie() function. Normally that function will store $this->userdata, but
		// in this case that array contains custom data, which we do not want in the cookie.
		$this->_set_cookie($cookie_userdata);
	}

	function sess_update()
	{
		// We only update the session every five minutes by default
		if (($this->userdata['last_activity'] + $this->sess_time_to_update) >= $this->now)
		{
			return;
		}

		// Save the old session id so we know which record to
		// update in the database if we need it
		$old_sessid = $this->userdata['session_id'];
		$new_sessid = '';
		while (strlen($new_sessid) < 32)
		{
			$new_sessid .= mt_rand(0, mt_getrandmax());
		}

		// To make the session ID even more secure we'll combine it with the user's IP
		$new_sessid .= $this->CI->input->ip_address();

		// Turn it into a hash
		$new_sessid = md5(uniqid($new_sessid, TRUE));

		// Update the session data in the session data array
		$this->userdata['session_id'] = $new_sessid;
		$this->userdata['last_activity'] = $this->now;
		
		// hack to set user id if already login
		$me = $this->CI->session->userdata('me');
		$me = (isset($me['id']) && $me['id'] != 0) ? $me['id'] : 0;
		$this->userdata['user_id'] = $me;
		

		// _set_cookie() will handle this for us if we aren't using database sessions
		// by pushing all userdata to the cookie.
		$cookie_data = NULL;

		// Update the session ID and last_activity field in the DB if needed
		if ($this->sess_use_database === TRUE)
		{
			
      // set cookie explicitly to only have our session data
			$cookie_data = array();
			foreach (array('session_id','ip_address','user_agent','last_activity','user_id') as $val)
			{
				$cookie_data[$val] = $this->userdata[$val];
			}

			$this->CI->db->query($this->CI->db->update_string($this->sess_table_name, array('last_activity' => $this->now, 'session_id' => $new_sessid, 'user_id' => $me), array('session_id' => $old_sessid)));
		}

		// Write the cookie
		$this->_set_cookie($cookie_data);
	}


}