Genus who came up with "Self Destruct Code" & "Copy Protection"

Hey guys, Special greetings to all my new pals on the list, you know who you are. I thank the dude who started this topic as I am pretty sure nearly everyone has faced clients who after getting the finished product thinks that he "over priced" the project or plain and simple wants to prove that he is a son of a whori*g b*tc*. Basically I am a java programmer and for the web I used to use/used servlets as jsp hosting is still a bit rare and pretty expensive.... anyway, coming into PHP does present a problem which i didnt face in java servlets... With java servlets you give the bytecode in .class files (I know they can be "broken" but there are differient methods to work around this.some good) but php you actually give readable code..which from my standpoint as a developer is a problem. After looking at all the suggestions i think the best one (which is legal) is to keep some vital files on your own server and after client pays to modify them accordingly, as changing the usernames/passwords/ftp access can be all that hard for them,and you would be totally screwed. The best solution that comes to mind of course is somehow to crash the whole damn webserver that your client is using.....but unfortunately that aint legal :-( ....that would certainly be satisfying though....almost as good as sex. As any good developer out there knows, first you call them "new friends" then "clients" and sometimes it goes to "S.O.Bs" and "bast**ds" and the worst part for me is I am not in the states but offer services to a lot of U.S clients so a actual contract is pretty much out of the question. I thank the dude again who posted this topic. If any of you guys have a better solution please do drop me a line. Have a great day, -Ryan.