saving items to the session in class

[webnick]

I'm trying to get a class to save arrays to the session and reload those from a database after logging in. I'm not much of a OOP coder so any help with this would be appreciated. It would have been much easier to just write the arrays to a database directly but I'm a little to far along for a re-write.

After constructing the class, the old session vars _are found in retrievePersistentMessages() but the buildMessages() shows $this->message_message as null there. Any ideas? Thanks!

class UserMessages
{
        static $error_levels = array('notice', 'warning', 'error');
        private $session;
        public $message_pointer, $message_persistence, $message_message, $message_page_element, $message_level;
        const store = 'system_messages';
        const store_js = 'system_messages_js';    

function __construct($message = null, $page_element = null, $class = null)
        {
                $this->message_pointer = rand();
                $this->message_persistence = 1;
                $this->message_message = $message;
                $this->message_page_element = $page_element;
                $this->message_level = in_array($class, self::$error_levels) ? $class : self::$error_levels[0];
                $this->session = Session::getInstance();

            if($this->message_message || $this->message_page_element) {
                    $this->buildMessages();
            }
            if($this->session->user_id) {
                    $this->retrievePersistentMessages();
            }
    }
    private function buildMessages()
    { // called after changing parameters
            $messages = $this->session->{self::store};
            $messages[ $this->message_pointer ] = array (
                    'pointer' => $this->message_pointer,
                    'persistence' => $this->message_persistence,
                    'level' => $this->message_level,
                    'page_element' => $this->message_page_element,
                    'message' => $this->message_message,
            );
            $this->session->{self::store} = $messages;
            $this->session->{self::store_js} = $messages;
            return $this;
    }
   function removeMessages($which = null)
    { // called after display
            $which = ($which == 'js') ? self::store_js : self::store;
            $messages = $this->session->{$which};
            foreach($messages as $pointer => $v) {
                    $timestamp = $messages[$pointer]['persistence']--;
                    if($timestamp <= 1 || $timestamp > 86400 && $timestamp < time())
                    { // delete these
                            unset($messages[$pointer]);
                    }
            }
            $this->session->{$which} = $messages;  // resave the session with messages left
            $this->savePersistentMessages();
    }
    function savePersistentMessages()
    { // called after remove
            if(empty($this->session->user_id)) {
                    return;
            }
            $messages = $this->session->{self::store};
            foreach($messages as $pointer => $arr) {
                    if($messages[$pointer]['persistence']) {
                            $store[ $pointer ] = $messages[ $pointer ];
                    }
            }
            if(!empty($store)) {
                    DataStorage::addData('userMessages', $this->session->user_id, serialize($store));
            }
    }
    function retrievePersistentMessages()
    { // called by init
            if(empty($this->session->user_id)) {
                    return;
            }
            $old_messages = DataStorage::findData('userMessages', $this->session->user_id);
            $old_messages_cleanup = DataStorage::deleteData('userMessages', $this->session->user_id);
            if(!empty($old_messages->data))
            {
                    $store = unserialize($old_messages->data);
                    foreach($store as $arr) {
                            foreach($arr as $key => $value) {
                                    $this->message_{$key} = $value; // rebuild messages from array
                            }
                    $this->buildMessages();
                    }
            }
    }