Erwin, I think he means by simply visiting any site that is coding in PHP, then like viewing the source for it in HTML, you could see the PHP coding.
When saving a PHP file, it doesn't just save the part that is HTML, it saves the output of the PHP script..which is just a bunch of echo functions creating HTML. I would think to download PHP files from websites that use it would be illegal, since you are viewing coded script of somebody else?s work..and could easily be ripped. Viewing HTML source is different in some ways, in that it's created to exactly what that page looks like..although, to be honest I'm not totally sure.
Uh, anyway, I'll conclude since I'm probably drifting off topic.