why my class doesn't work?

[ice_berg16]

i create a class to access mysql,(named mysql.inc.php)
but it display nothing
when i use this class create a test page which named test.php
please help me
the follow is class code

<?php
/************************
mysql database driver
create by ice_berg16
at 2003.12.10
************************/
class db_mysql
{
var $host = "";
var $user = "";

var $pwd = "";
var $db_name = "";
var $link_id = 0;
var $query_id = 0;
var $errno = 0;
var $error = "";
var $record = array();
//function list

/* constructor
*/
function db_mysql()
{
	$this->host = "localhost:3306";
	$this->user = "root";
	$this->pwd  = "format";
	$this->db_name = "mysite";
}
/********function connect************
*********return 0 :error ************
*********return link_id :ok ********/
function connect($host, $user, $pwd, $db_name)
{
	if("" == $host)
		$host = $this->host;
	if("" == $user)
		$user = $this->user;
	if("" == $pwd)
		$pwd = $this->pwd;
	if("" == $db_name)
		$db_name = $this->db_name;
	//now connect to the database
	$this->link_id = mysql_connect($host, $user, $pwd);
	if(!$this->link_id)
	{
		$this->halt();
		return 0;
	}
	if(!mysql_select_db($db_name, $this->link_id))
	{
		$this->halt();
		return 0;
	}
	return $this->link_id;			
}

/****function query************
*****return 0 : error**********
******************************/
function query($sql)
{
	if(!$this->link_id)
	{
		$this->halt("no connect is active.");
		return 0;
	}
	if("" == $sql)
	{
		$this->halt("the query string is empty.");
		return 0;
	}
	$this->query_id = mysql_query($sql, $this->link_id);
	if(!$this->query_id)
	{	
		$this->halt();
		return 0;
	}
	return $this->query_id;
}

/****function get_record***
*****return 0 : error******
*****return one record****/
function get_record()
{
	if(!$this->link_id || !$this ->query_id)
	{
		$this->halt("no query record.");
		return 0;
	}
	$this->record = mysql_fetch_array($this->query_id);
	if(!$this->record)
	{
		$this->halt("get record failed.");
		return 0;
	}
	return $this->record;
} 
/****function get_data()********
*****return 0 : error***********
*****return data in the record*/
function get_data($id)
{
	return $this->record[$id];
}
/***fucntion total_record()***
****get the number of the*****
****record********************/
function total_record()
{
	return mysql_num_rows($this->query_id);
}
/* if the operate is success
** can be used afer insert,update,delete etc.
** can not use when query is "select"
*/
function success()
{
	if (mysql_affected_rows($this->link_id))
		return 1;
	else
		return 0;
}
/* close the connect to the mysql server
*/
function close()
{
	mysql_close();
}
/****function halt*********
*****process all error*****
*****and echo the error***/
function halt($err_msg="")
{
	if("" == $err_msg)
	{
		$this->errno = mysql_errno();
		$this->error = mysql_error();
		echo "mysql error:\n";
		echo $this->errno.":".$this->error;
	}
	else
	{
		echo "mysql error:\n";
		echo $err_msg;
	}
}

}
?>

//***the follow is the test page************//

<?php
require("class/mysql.inc.php");
var $db = new db_mysql();
if(!$db->connect())
echo "error: connect";
$sql="select * from printer";
if(!$db->query($sql))
echo "error: query";
while($db->get_record())
{
echo $db->get_data("id")."<br>";
echo $db->get_data("brand")."<br>";
}

?>

[olaf]

Hallo,

first of all what is this:

if("" == $sql)

this means: if nothing equal to $sql

???

[ahundiak]

I'm guessing you are getting an error (be nice if you explained what was failing) after:
var $db = new db_mysql();

The var is incorrect. Only use that for class instance data. Plus db_mysql expectes 4 arguments, you need to give them default values to make them optional.

And I suspect there are many other little problems. Strip out everything but the constructor, get it working then add in one method at a time (connect, query, fetch etc) and get them working.

[ice_berg16]

thank u for your help

olaf:

do u think use the if(!$sql)...will be better?

are there any diferences ?

ahundiak:

i cant understand what's your means?
do i make an error when i declare the class instance?
can u tell me the right sytax?

[ice_berg16]

thanks
i have solved the problem,
i get rid of the var the code worked well.
but i dont know why?

[ahundiak]

error_reporting(E_ALL); // Make sure all syntax errors are reported
class db_mysql
{
  function db_mysql();
  {
  }
  function connect($user)
  {
  }
}
$db =& new db_mysql();
$db->connect();

See the error. The connect method expects an argument. It's not getting one and thus complaining. Start simple and work your way up.

[ice_berg16]

why add a "&" in the code $db = & new $db_mysql;

[ahundiak]

Look up references in the manual. You usually will want a reference to these sort of objects.