ช่วยแก้โค็ตให้หน่อย หน้าซื้อสินค้า มันไม่ส่งค่าที่เลือกไปอ่าครับ

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<?
			   require('conn_mysql.php');
		echo "<form action=555.php method=POST name=frmMain target=_blank><b>สินค้า:</b><select name=product onchange=frmMain.txtVol.value=this.value>";
	$sql = "select * from product order by product_name where product_name='$product_name' ";
	$first="";
	$result = mysql_query($sql);
	$array= mysql_fetch_array($result);
			if(!$first){ $first=$array[price]; }
	echo "<option class=style6  value=$array[product_name]>###--กรุณาเลือกสินค้า--###</option>";
	
	$sql = "select * from product order by product_name ";
	$result=mysql_query($sql);
		while($array = mysql_fetch_array($result))
	{				if(!$first){ $first=$array[product_price]; }
				echo "<option value =$array[product_price]>";
				echo " $array[product_name]<br>";
	}
	echo "</option></select>&nbsp;&nbsp;<b>ราคา:</b><input type=text name=txtVol size=20 value=$first readonly>";
	echo "</option></select>&nbsp;&nbsp;<b>จำนวน:</b><input type=text name=number value=></form></form>";
	echo "<br><input type=submit name=add value=ADD >";
	?>
    <iframe name="AA" frameborder="0" marginheight=" 0" marginwidth=" 0" height=" 0" width="0" scrolling="no" src="about:blank"></iframe>
<? echo $a;?>

<?
$x = $_POST["product"];
$b = $_POST["txtVol"];
$w = $_POST["number"];
$a = $b*$w;
echo = "$a";
echo "<script>window.parent.location='q.php?a=$a';</script>";
?>