how to "close" a php script for commercial use? [duplicate]

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Possible Duplicate:

PHP - protecting code

I have build a php "management" site for a client with some specific features v开发者_开发技巧ery usefull for their kind of business. So I decided with the client to sell to other companies this back-office software.

How can I close this php site so that clients ho buy it can install it only once and validate it with a key? also, can they just copy all files and db and give it to someone else?

What are the techniques to close a php site as a SaaS?

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You'll have to encode it (for example) with Ioncube or ZendGuard so they can't easily delete your checkings. However, remember, if they want to crack it, they will