title: Generating a truly unique order id in PHP?
body: <p>I'm considering using this: <a href="http://phpgoogle.blogspot.com/2007/08/four-ways-to-generate-unique-id-by-php.html" rel="nofollow noreferrer">http://phpgoogle.blogspot.com/2007/08/four-ways-to-generate-unique-id-by-php.html</a></p>
  
  <p>My idea is to use a mixture between 2 and 3. But my question is that, although the chances are small, is there still a chance that two orders with the same order # can be generated if I substring the result to be only 5 characters long? What about 3? 2? 1? Surely if it's 1, there is a 1/(26 + 10) chance that the id will be the same?</p>