Form with PHP

[Maury76]

I need to create a drop down box with the categories list of my forum.
How can I redirect the user to the correct page when a selection is made?

This is the attempt i made:

<?php
global $prefix, $user_prefix, $db, $sitename, $bgcolor0, $bgcolor1, $bgcolor2, $bgcolor3, $currentlang;
$content = "";
$content .= "<form name=\"info\">";
$content .= "<select size=\"1\" name=\"categoria\" onChange=\"document.location='modules?name=Forums&file=index&c='+[this.selectedIndex].value;\">"; 
$result = $db->sql_query("SELECT cat_id, cat_title FROM ".$prefix."_bbcategories ORDER BY cat_id");
while ($row = $db->sql_fetchrow($result))
	{
	 $content .= "<option value='$row[cat_id]'>$row[cat_title]</option>";
	}
$content .= "</select></form>";

?>

Thank's for your help... :p

[justsomeone]

What does this do wrong?

Sorry, I'm not great on the javascript side of things.

[Maury76]

When I select an option from the menu the server don't resolve the value variable...

I have this:

'modules?name=Forums&file=index&c=undefined

I don't understand where I wrong...