php选项值链接

Question

I created a dropdown menu and when click on the option on the category in the drop down bar, it can link to my product page, but i failed to linked them, does anyone know what is the problems in my code?

enter code here

$link=mysql_connect("localhost","root","")or die("Can't Connect...");
mysql_select_db("fyp",$link) or die("Can't Connect to Database...");
$query="select * from category ";
$res=mysql_query($query,$link);

while($row=mysql_fetch_assoc($res))
{
    echo "<option value='product.php category=".$roww['$cat_id']."'>".$row['cat_nm'];///here is the problem
    $qq = "select * from subcat where parent_id=".$row['cat_id'];
    $ress = mysql_query($qq,$link) or die("wrong delete subcat query..");
    while($roww = mysql_fetch_assoc($ress))
    {
        echo "<option value='".$roww['subcat_id']."'> ---> ".$roww['subcat_nm'];//here is the problems
    }

}

mysql_close($link);

?>

enter image description here

Answer 1

do it like this, give url you want to edirect to in value and add onchange() to <select>. And you have missed ? which server as query parameter,

 echo "<option value='product.php category=".$roww['$cat_id']."'>".$row['cat_nm'];///here is the problem
                                 ^

it shud be

echo "<option value='product.php?category=".$roww['$cat_id']."'>".$row['cat_nm'];///here is the problem
                                ^

and

<select onchange="this.options[this.selectedIndex].value && (window.location = this.options[this.selectedIndex].value);">
    <option value="">Select...</option>
    <option value="product.php?category=".$roww['$cat_id']."">Product 1</option>
    <option value="product.php?category=".$roww['$cat_id']."">Prosuct 2</option>
</select>