How to generate unique numbers/IDs without duplicates? [duplicate]

This question already has answers here: Closed 11 years ago.

Possible Duplicate:

PHP: How to generate a random, unique, alphanumeric string?

I wish to generate Product Keys or Licenses using PHP. Is there a function that allow me to do generate unique numbers/IDs but at the same time make sure that there won't 开发者_运维百科be a chance for duplicate?

Thank you.

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You could use php's uniqid function to generate id's:

http://www.php.net/manual/en/function.uniqid.php

or leave that responsibility to the database engine, which will generate auto-incremented id values.

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Use a uniqid

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You can use md5(timestamp), its always unique