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POWill using a substring of an MD5 hash like this be unique enough?
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copied!<p>What I am trying to do is create a 12 character id for articles on my website similar to how youtube handles their video id (<a href="http://www.youtube.com/watch?v=53iddd5IcSU" rel="nofollow noreferrer">http://www.youtube.com/watch?v=53iddd5IcSU</a>). Right now I am generating an MD5 hash and then grabbing 12 characters of it like this:</p> <pre><code>$ArticleId = substr(MD5("Article".$currentID),10,12) </code></pre> <p>where $currentID is the numeric ID from the database (eg 144)</p> <p>I am slightly paranoid that I will run into a duplicate $ArticleId, but realistically what are the chances that this will happen? And also, being that the column in my database is unique, how can I handle this rare scenario without having an ugly error thrown?</p> <p>P.S. I made a small script to check for duplicates within the first 5000 $ArticleId's and there were none.</p> <p>EDIT: I don't like the way the base64_encode hashes look so I did this:</p> <pre><code>function retryAID($currentID) { $AID = substr(MD5("Article".$currentID*2),10,12); $setAID = "UPDATE `table` SET `artID` = '$AID' WHERE `id` = $currentID "; mysql_query($setLID) or retryAID($currentID); } $AID = substr(MD5("Article".$currentID),10,12); $setAID = "UPDATE `table` SET `artID` = '$AID' WHERE `id` = $currentID "; mysql_query($setAID) or retryAID($currentID); </code></pre> <p>Since the AID column is unique the mysql_query will throw an error and the retryAID function will find a unique id...</p>

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