what gives mysql_result

[omegared]

Hello,
I am scratching my head on this one. I have a function that generates a drop down menu (it has been simplified below).

my issue is with the mysql_result function where I would like to use the $option_value and $option_display parameters. It works fine if I hard code in 0 and 1 instead of the variable.

My question is simple, why and how do I fix it.
Thank you in advance

function ddm($type, $option_value='0', $option_display='1', $name, $default='', $tabindex=''){
conn_db();
$sql = "";

switch($type){
	case "group":
	$sql .= ('SELECT * FROM student_groups ');
	break;

	case "grade":
	$sql .= ('SELECT * FROM student_grades');
	break;
}

if(!($result_ddm = mysql_query($sql))){
	die('error utils.inc function drop_menu '.mysql_error());
}

$select .= '<select name="'.$name.'" id="'.$name.'" tabindex="'.$tabindex.'">';

for ($i=0; $i < mysql_numrows($result_ddm); $i++) {
	$opt_code = mysql_result($result_ddm, $i, $option_value); //THIS DOES NOT WORK
	$opt_desc = mysql_result($result_ddm, $i, $option_display); //THIS DOES NOT WORK

	//$opt_code = mysql_result($result_ddm, $i, '0'); THIS WORKS
	//$opt_desc = mysql_result($result_ddm, $i, '1'); THIS WORKS

	$select .= '<option value="'.$opt_code.'"';

	$select .=  ">$opt_desc</option>";
}

$select .= "</select>\n";
return($select);

}

[devinemke]

function ddm($type, $option_value = '0', $option_display = '1', $name, $default = '', $tabindex = '')
{
	conn_db();

$sql = 'SELECT opt_code, opt_desc FROM student_' . $type . 's';
$result = mysql_query($sql) or exit(mysql_error());

if (mysql_num_rows($result))
{
	$select = '<select name="'. $name . '" id="' . $name . '" tabindex="' . $tabindex . '">';
	while ($row = mysql_fetch_assoc($result))
	{
		$select .= '<option value="' . $row['opt_code'] . '">' . $row['opt_desc'] . '</option>';
	}
	$select .= '</select>';

	return $select;
}
else
{
	return false;
}
}