Replicating old ASP code into PHP

I've got a script that was created in ASP and now I need to use it in PHP.

It's basically populating a navigation and sub navigation. The initial navigation is populated by a table called category and the subnav is populated by a table called subcat.

The structure is something like this:

Home
Products
     item1
     item2
     item3
     item4
Services
     serv1
     serv2
     serv3
     serv4
About
Contact

I've got it to work to an extent, but the subnav is showing on each when it should only be showing on the particular category.

I've attached 2 jpegs, the first is how the nav used to work in ASP, and the second is the PHP version.

Here is my ASP code, PHP code in code box:
<%
Dim RSnav
Dim RSnav_numRows

Set RSnav = Server.CreateObject("ADODB.Recordset")
RSnav.ActiveConnection = MM_hill_STRING
RSnav.Source = "SELECT * FROM category"
RSnav.CursorType = 0
RSnav.CursorLocation = 2
RSnav.LockType = 1
RSnav.Open()

RSnav_numRows = 0
%>

<%
Dim RSsubcat__MMColParam
RSsubcat__MMColParam = "1"
If (Request.QueryString("cat") <> "") Then
  RSsubcat__MMColParam = Request.QueryString("cat")
End If
%>
<%
Dim RSsubcat
Dim RSsubcat_numRows

Set RSsubcat = Server.CreateObject("ADODB.Recordset")
RSsubcat.ActiveConnection = MM_hill_STRING
RSsubcat.Source = "SELECT * FROM subcat WHERE category = " + Replace(RSsubcat__MMColParam, "'", "''") + ""
RSsubcat.CursorType = 0
RSsubcat.CursorLocation = 2
RSsubcat.LockType = 1
RSsubcat.Open()

RSsubcat_numRows = 0
%>
<%
Dim Repeat1__numRows
Dim Repeat1__index

Repeat1__numRows = -1
Repeat1__index = 0
RSnav_numRows = RSnav_numRows + Repeat1__numRows
%>
<%
Dim Repeat3__numRows
Dim Repeat3__index

Repeat3__numRows = -1
Repeat3__index = 0
RSsubcat_numRows = RSsubcat_numRows + Repeat3__numRows
%>


<ul class="subnav">
        <%
While ((Repeat1__numRows <> 0) AND (NOT RSnav.EOF))
            ID = RSnav.Fields.Item("categoryID").Value
%>
            <% If ID = request.querystring("cat") + 0 Then %>
        <li class="open_nav"><%=(RSnav.Fields.Item("categoryName").Value)%>
            <% else %>
        <li><a href="products-list.asp?cat=<%=(RSnav.Fields.Item("categoryID").Value)%><% if RSnav.Fields.Item("categoryFirst").Value <> "" then %>&amp;sub=<%=RSnav.Fields.Item("categoryFirst").Value%><% end if %>"><%=(RSnav.Fields.Item("categoryName").Value)%></a>
            <% end if %>
                        <ul>
            <% If Repeat1__index = request.querystring("cat") -1 Then
            While ((Repeat3__numRows <> 0) AND (NOT RSsubcat.EOF))
            subID = RSsubcat.Fields.Item("subcatID").Value
            %>
                        <% If subID = request.querystring("sub") + 0 Then %>
                          <li><%=(RSsubcat.Fields.Item("subcatName").Value)%></li>
                        <% else %>
                          <li><a href="products-list.asp?cat=<%=request.querystring("cat")%>&amp;sub=<%=(RSsubcat.Fields.Item("subcatID").Value)%>"><%=(RSsubcat.Fields.Item("subcatName").Value)%></a></li>
                        <% end if %>
                          <%
              Repeat3__index=Repeat3__index+1
              Repeat3__numRows=Repeat3__numRows-1
              RSsubcat.MoveNext()
            Wend
            end if
            %>
            </ul>
        <%
  Repeat1__index=Repeat1__index+1
  Repeat1__numRows=Repeat1__numRows-1
  RSnav.MoveNext()
Wend
%>
       
      </ul>

Thanks

Chris

<ul class="subnav">
      <?php do {
	  $ID = $row_RSnav['categoryID'];
	  ?>
      <?php if ($ID = $_GET['cat'] + "0") { ?>
        <li class="open_nav"><?php echo $row_RSnav['categoryName']; ?>
        <? } else { ?>
        <li><a href="products-list.php?cat=<?php echo $row_RSnav['categoryID']; ?><?php if ($row_RSnav['categoryFirst'] != "") { ?>&amp;sub=<?php echo $row_RSnav['categoryFirst']; ?><?php } ?>"><?php echo $row_RSnav['categoryName']; ?></a>
        <?php } ?>
          <ul>
            <?php do {
			$subID = $row_RSsubcat['subcatID'];
			?>
      		<?php if ($subID = $_GET['sub'] + "0") { ?>
            <li><a href="#"><?php echo $row_RSsubcat['subcatName']; ?></a></li>
        	<? } else { ?>
			<li><a href="products-list.php?cat=<?php echo $_GET['cat']; ?>&amp;sub=<?php echo $row_RSsubcat['subcatID']; ?>"><?php echo $row_RSsubcat['subcatName']; ?></a></li>
        	<?php } ?>
            <?php } while ($row_RSsubcat = mysql_fetch_assoc($RSsubcat)); ?>
          </ul>
        </li>
        <?php } while ($row_RSnav = mysql_fetch_assoc($RSnav)); ?>
    </ul>

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