Making things 'tamper proof'

Hi all,

I am busy developing some applications which will be sold, once complete.
The .php files, as far as I know, have to be distributed as they are (in
source code). Is there any way to protect the application so that it can not
be tampered with? Can I write some stored procedure of some sort which
prevents people from messing with the code?

Best regards,
Chris



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