How to pass variable from hidden input box to another page - asp-classic

Question

I am trying to get a value from a hidden input text box to another page, but it doesn't work. How to pass variable from hidden input box to another page?
Page1.asp
<input type="hidden" name="FormID" value="<% objRS("Form_id")%>
...
<input type="hidden" name="FormID" value="<%= nFormID %>">
<input type="button" value="Open Page2" onclick=openwin();"/>
Page2.asp
<%
iFormID = Request.Form("FormID")
sSQL = "select * from Form where Form_id = " & iFormID
When I click on the Button Open Page2, it doesn't get the value of FormID.
How do I fix it to get the FormID from Page1.asp?
Updated: when I tried to add a button with this JS, it won't get the variable from Page1.asp
I added this on page1.asp:
function openwin()
{window.open("Page2.asp","mywindow","width=500,height=400"):}
<input type="hidden" name="FormID" value="<%= nFormID %>">
<input type="button" value="Open Page2" onclick=openwin();"/>
Thanks.

Answer 1

Since it seems like you're trying to open up a pop up window, I've added a second answer, as you are not actually POSTing any data. if you want to use a pop up, the easiest way is to put the data in the query string, like so:
function openwin()
{window.open("Page2.asp?formID=" + document.frmReport.FormID.value, "mywindow","width=500,height=400"):}
now, i notice you're using a loop to generate the formIDs and using the same NAME for each field. so you'll need to loop through the set of fields, grab each ones value, and send it along as one string in the query string:
function openwin() {
var ids = '';
for( var index = 0; index < document.frmReport.FormID.length; index++ ) {
if( ids == '' )
ids += document.frmReport.FormID[ index ].value;
else
ids += ',' + document.frmReport.FormID[ index ].value;
}
window.open("Page2.asp?FormIDs=" + ids,"mywindow","width=500,height=400");
}
and on Page2.asp, you would do:
iFormIDs = Request.QueryString("FormIDs")
sSQL = "select * from Form where Form_id in ( " & iFormIDs & " ) "
You'll notice that I changed the sql to use the IN clause, that way you can get ALL records for a given set of formIDs, even if it's just one. This obviously doesn't take into account any security precautions to prevent sql injection, but this should get you started.

Answer 2

first, make sure your elements are in a form block with a METHOD of POST
second, your element
<input type="hidden" name="FormID" value="<% objRS("Form_id")%>
needs to be
<input type="hidden" name="FormID" value="<%= objRS("Form_id")%>" />
<%= is shorthand for Response.Write
so page1 would look like:
<form name="myForm" method="post" action="page2.asp">
<input type="hidden" name="FormID" value="<%= objRS("Form_id")%>" />
...
<input type="hidden" name="FormID" value="<%= nFormID %>">
<input type="submit" value="Open Page2" />
</form>