Zebra_Session::read PHP Méthode

    function read($session_id)
    {
        // get the lock name, associated with the current session
        $this->session_lock = $this->_mysql_real_escape_string('session_' . $session_id);
        // try to obtain a lock with the given name and timeout
        $result = $this->_mysql_query('SELECT GET_LOCK("' . $this->session_lock . '", ' . $this->_mysql_real_escape_string($this->lock_timeout) . ')');
        // if there was an error
        // stop execution
        if (!is_object($result) || strtolower(get_class($result)) != 'mysqli_result' || @mysqli_num_rows($result) != 1 || !($row = mysqli_fetch_array($result)) || $row[0] != 1) {
            die('Zebra_Session: Could not obtain session lock!');
        }
        //  reads session data associated with a session id, but only if
        //  -   the session ID exists;
        //  -   the session has not expired;
        //  -   if lock_to_user_agent is TRUE and the HTTP_USER_AGENT is the same as the one who had previously been associated with this particular session;
        //  -   if lock_to_ip is TRUE and the host is the same as the one who had previously been associated with this particular session;
        $hash = '';
        // if we need to identify sessions by also checking the user agent
        if ($this->lock_to_user_agent && isset($_SERVER['HTTP_USER_AGENT'])) {
            $hash .= $_SERVER['HTTP_USER_AGENT'];
        }
        // if we need to identify sessions by also checking the host
        if ($this->lock_to_ip && isset($_SERVER['REMOTE_ADDR'])) {
            $hash .= $_SERVER['REMOTE_ADDR'];
        }
        // append this to the end
        $hash .= $this->security_code;
        $result = $this->_mysql_query('

            SELECT
                session_data
            FROM
                ' . $this->table_name . '
            WHERE
                session_id = "' . $this->_mysql_real_escape_string($session_id) . '" AND
                session_expire > "' . time() . '" AND
                hash = "' . $this->_mysql_real_escape_string(md5($hash)) . '"
            LIMIT 1

        ') or die($this->_mysql_error());
        // if anything was found
        if (is_object($result) && strtolower(get_class($result)) == 'mysqli_result' && @mysqli_num_rows($result) > 0) {
            // return found data
            $fields = @mysqli_fetch_assoc($result);
            // don't bother with the unserialization - PHP handles this automatically
            return $fields['session_data'];
        }
        $this->regenerate_id();
        // on error return an empty string - this HAS to be an empty string
        return '';
    }