Mage_Core_Model_Resource_Session::setSaveHandler PHP Method

    public function setSaveHandler()
    {
        if ($this->hasConnection()) {
            session_set_save_handler(array($this, 'open'), array($this, 'close'), array($this, 'read'), array($this, 'write'), array($this, 'destroy'), array($this, 'gc'));
        } else {
            session_save_path(Mage::getBaseDir('session'));
        }
        return $this;
    }