Validating PHP dropdown menu

[Natsu]

Im trying to make it so that each course can only be selected once, so let's say I select math for the first course, it should not be in the next dropdown menu. So only 1 of each course can be chosen.

Here is the code: http://pastebin.com/zUaEXbPS

[Zren]

May the heathen gods smite you for this:

php:

<?php for ($i=0;$i<101;$i++)                 {                 echo "<option value=\"".$i."\">".$i."</option>";                 }      ?>

What's wrong with a textbox? What are your reasons specifically for using a drop down box for this data field?

The formatting of this code makes my head hurt. Anyways. Selecting a option is a client side event that happens after the server finishes generating the page. This is something that should be done with client side scripting.

[iso]

Javascript is necessary.

Also, you really shouldn't be using tables or inline styling.