How do I use a PHP file in root directory with relative paths for other pages?

[semperfi]

I asked this question the other day:http://stackoverflow.com/questions/15714842/how-can-i-call-html-inside-a-div-from-a-single-location, etc.But I have a feeling there is a better way to do this.I also thought about putting the header PHP in each directory, but I figure that defeats the purpose of easily editing 1 file to change them all.The other idea is to put everything into one directory, but I don't want to do that.So what am I missing? Thanks.