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    copied!<p>I wrote a tiny lib to generate obfuscated hashes from integers.</p> <p><a href="http://web.archive.org/web/20130727034425/http://blog.kevburnsjr.com/php-unique-hash" rel="noreferrer">http://web.archive.org/web/20130727034425/http://blog.kevburnsjr.com/php-unique-hash</a></p> <pre><code>$ids = range(1,10); foreach($ids as $id) { echo PseudoCrypt::unhash($id) . "\n"; }</code></pre> <pre>m8z2p 8hy5e uqx83 gzwas 38vdh phug6 bqtiv xzslk k8ro9 6hqqy</pre> <p>7/14/2015: Adding the actual code below, since it has become difficult to find:</p> <pre><code>&lt;?php /** * PseudoCrypt by KevBurns (http://blog.kevburnsjr.com/php-unique-hash) * Reference/source: http://stackoverflow.com/a/1464155/933782 * * I want a short alphanumeric hash that’s unique and who’s sequence is difficult to deduce. * I could run it out to md5 and trim the first n chars but that’s not going to be very unique. * Storing a truncated checksum in a unique field means that the frequency of collisions will increase * geometrically as the number of unique keys for a base 62 encoded integer approaches 62^n. * I’d rather do it right than code myself a timebomb. So I came up with this. * * Sample Code: * * echo "&lt;pre&gt;"; * foreach(range(1, 10) as $n) { * echo $n." - "; * $hash = PseudoCrypt::hash($n, 6); * echo $hash." - "; * echo PseudoCrypt::unhash($hash)."&lt;br/&gt;"; * } * * Sample Results: * 1 - cJinsP - 1 * 2 - EdRbko - 2 * 3 - qxAPdD - 3 * 4 - TGtDVc - 4 * 5 - 5ac1O1 - 5 * 6 - huKpGQ - 6 * 7 - KE3d8p - 7 * 8 - wXmR1E - 8 * 9 - YrVEtd - 9 * 10 - BBE2m2 - 10 */ class PseudoCrypt { /* Key: Next prime greater than 62 ^ n / 1.618033988749894848 */ /* Value: modular multiplicative inverse */ private static $golden_primes = array( '1' =&gt; '1', '41' =&gt; '59', '2377' =&gt; '1677', '147299' =&gt; '187507', '9132313' =&gt; '5952585', '566201239' =&gt; '643566407', '35104476161' =&gt; '22071637057', '2176477521929' =&gt; '294289236153', '134941606358731' =&gt; '88879354792675', '8366379594239857' =&gt; '7275288500431249', '518715534842869223' =&gt; '280042546585394647' ); /* Ascii : 0 9, A Z, a z */ /* $chars = array_merge(range(48,57), range(65,90), range(97,122)) */ private static $chars62 = array( 0=&gt;48,1=&gt;49,2=&gt;50,3=&gt;51,4=&gt;52,5=&gt;53,6=&gt;54,7=&gt;55,8=&gt;56,9=&gt;57,10=&gt;65, 11=&gt;66,12=&gt;67,13=&gt;68,14=&gt;69,15=&gt;70,16=&gt;71,17=&gt;72,18=&gt;73,19=&gt;74,20=&gt;75, 21=&gt;76,22=&gt;77,23=&gt;78,24=&gt;79,25=&gt;80,26=&gt;81,27=&gt;82,28=&gt;83,29=&gt;84,30=&gt;85, 31=&gt;86,32=&gt;87,33=&gt;88,34=&gt;89,35=&gt;90,36=&gt;97,37=&gt;98,38=&gt;99,39=&gt;100,40=&gt;101, 41=&gt;102,42=&gt;103,43=&gt;104,44=&gt;105,45=&gt;106,46=&gt;107,47=&gt;108,48=&gt;109,49=&gt;110, 50=&gt;111,51=&gt;112,52=&gt;113,53=&gt;114,54=&gt;115,55=&gt;116,56=&gt;117,57=&gt;118,58=&gt;119, 59=&gt;120,60=&gt;121,61=&gt;122 ); public static function base62($int) { $key = ""; while(bccomp($int, 0) &gt; 0) { $mod = bcmod($int, 62); $key .= chr(self::$chars62[$mod]); $int = bcdiv($int, 62); } return strrev($key); } public static function hash($num, $len = 5) { $ceil = bcpow(62, $len); $primes = array_keys(self::$golden_primes); $prime = $primes[$len]; $dec = bcmod(bcmul($num, $prime), $ceil); $hash = self::base62($dec); return str_pad($hash, $len, "0", STR_PAD_LEFT); } public static function unbase62($key) { $int = 0; foreach(str_split(strrev($key)) as $i =&gt; $char) { $dec = array_search(ord($char), self::$chars62); $int = bcadd(bcmul($dec, bcpow(62, $i)), $int); } return $int; } public static function unhash($hash) { $len = strlen($hash); $ceil = bcpow(62, $len); $mmiprimes = array_values(self::$golden_primes); $mmi = $mmiprimes[$len]; $num = self::unbase62($hash); $dec = bcmod(bcmul($num, $mmi), $ceil); return $dec; } } </code></pre>
 

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