Sure, but I am thinking you want to update one select box based on the value of another... If you are using hard coded values, this is no big deal, but would still require the use of javasciript, and php doesn't come into play at all.
If the drop-down values are stored in a table, then you would need to write a query to get the data anyhow, but you still need javascript to reload the page in order to query the table...
Either way, javascript is a necessity...