MySQL database abstraction class in PHP

class DBI
{
    var $server;
    var $user;
    var $pass;
    var $db;
    var $link;
    var $result = null;

    /*
    ** The constrcutor, terminates the script if the connection fails
    ** @params:
    ** string $server - the server IP or hostname
    ** string $user - the username 
    ** string $pass - the password
    ** string $db - the name of the database to use
    */

    function DBI($server,$user,$pass,$db)
    {
        $this->server   =  $server;
        $this->user  =    $user;
        $this->pass  =    $pass;
        $this->db      =  $db;
        if(!$this->connect())
        {
            die("<div style=\"text-align:center;border:#a00 solid 1px;padding:4px 1px;margin:0 3px 5px 3px;background:#fdd;color:#a00;font-size:12px;font-family:georgia;letter-spacing:1px;width:90%;\">Server is not reachable ($user@$server)</div>");
        }
    }

    /*
    ** A method which connects to the server. This cannot be called statically.
    ** @return: boolean
    */
    function connect()
    {
        if($this->link=mysql_connect($this->server,$this->user,$this->pass,true))
            if(mysql_select_db($this->db,$this->link))
                return true;
        if(is_resource($this->link))
            print("<div class=\"error-box\">".mysql_error($this->link)."</div>");
        return false;
    }

    /*
    ** Queries the DB
    ** @param:
    ** string $query - the SQL query
    ** boolean $debug - terminates on failure if set to true
    ** @return: boolean - true if successful, else false
    */
    function query($query,$debug=false)
    {
        if($debug)
        {
            $this->result=mysql_query($query,$this->link) or die("<div class=\"error-box\">".mysql_error($this->link)."$query</div>");
        }
        else
        {
            if($this->result=mysql_query($query,$this->link))
                return true;
            return false;
        }
            
    }

    /*
    ** Fetches rows from the resultset
    ** @param:
    ** PHP Constant $type - MYSQL_NUM (default) / MYSQL_ASSOC
    */
    function fetch_rows($type=MYSQL_NUM)
    {
        return mysql_fetch_array($this->result,$type);
    }

    /*
    ** Returns the no. of rows returned
    */
    function num_rows()
    {
        return mysql_num_rows($this->result);
    }

    /*
    ** Frees the memory of the resultset
    */
    function free_r()
    {
        mysql_free_result($this->result);
    }

    /*
    ** Returns the last insert ID, for an auto_increment field
    */
    function insert_id()
    {
        return mysql_insert_id($this->link);
    }

    /*
    ** Closes the MySQL connecttion
    */
    function close()
    {
        mysql_close($this->link);
    }
}

$db = new DB("server.com","admin","pass","customer_db");
$sql = "SELECT * FROM customers";
$db->query($sql);
// Number of rows returned
printf("The number of rows returned = %d \n<br/>",$db->num_rows());

while($row=$db->fetch_rows())
{
    printf('$row[0] = %s\n',$row[0]);
}