Not entirely seeing the connection between radio buttons and htmlentities?
htmlentities changes the various characters such as > and < which mean something in
HTML into entities which tell the web browser, these aren't the beginning and end of tags but
actually mean print a > or < etc. onto the page.
You don't generally need to use htmlentities() on user input and it is absolutely not a good
way to validate the data for security if that's what you're trying to do.
A radio button will generally send back whatever value was selected, so in the example below
if someone selected the first radio button then it'd send back the value "YES".
Might be getting the wrong end of the stick mind you...