PHP in Single Event Page?

Hi,

I want to know how I can use PHP in the single event format page,
Currently I display 3 sets of information for an event, however if one set is not filled in, i’d like to bypass that section, basically if length of field<0 then don’t create the placeholders.

However I don’t seem to be able to use PHP in the Single Event format field, is there a way to complete what I’m after?

Any help is greatly appreciated.

Thanks.