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POUnderstanding a url shortener function
 

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    <p>I am trying to better understand how a function works. I am not familiar with how the function below works and I was looking for some help and possibly an explanation. I get most of it except one part that uses math functions like floor(). The part that confuses me the most is the do...while loop. How exactly does using $id, floor() and $base convert a long url into a short url? Also, what exactly is it iterating through where you need a do...while loop to do it?</p> <pre><code>$chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'; $base = strlen($chars); // base 62 $site = 'http://short.co'; // Replace with your domain // ...Connect to MySQL server here... function shorten_url($url) { global $chars, $site, $base; $hash = md5($url); $alnum = NULL; // // Check if URL is already exist on db // Otherwise add this URL to table $res = mysql_query("SELECT id FROM urls WHERE url_hash='$hash'"); if (mysql_num_rows($res)) { $row = mysql_fetch_object($res); $id = $row-&gt;id; } else { mysql_query("INSERT INTO urls (url, url_hash) VALUES ('$url', '$hash')"); $id = mysql_insert_id(); } // Convert id to base 62 and decode to alphanumeric do { $alnum = $chars[($id%$base)].$alnum; } while ($id = floor($id/$base)); return "$site/$alnum"; } </code></pre> <p>If someone could provide an explanation without a ton of math jargon...I would appreciate it. Thanks.</p> <p>I got the function from: <a href="http://bsd-noobz.com/blog/how-to-create-url-shortening-service-using-simple-php" rel="nofollow">http://bsd-noobz.com/blog/how-to-create-url-shortening-service-using-simple-php</a></p>
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