PHP数字和字符串ID互转函数（类似优酷ID）

* @author Simon Franz * @author Deadfish * @copyright 2008 Kevin van Zonneveld (http://kevin.vanzonneveld.net) * @license http://www.opensource.org/licenses/bsd-license.php New BSD Licence * @version SVN: Release: $Id: alphaID.inc.php 344 2009-06-10 17:43:59Z kevin $ * @link http://kevin.vanzonneveld.net/ * * @param mixed $in String or long input to translate * @param boolean $to_num Reverses translation when true * @param mixed $pad_up Number or boolean padds the result up to a specified length * @param string $passKey Supplying a password makes it harder to calculate the original ID * * @return mixed string or long */ function alphaID($in,$to_num = false,$pad_up = false,$passKey = null) { $index = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; if ($passKey !== null) { // Although this function's purpose is to just make the // ID short - and not so much secure, // with this patch by Simon Franz (http://blog.snaky.org/) // you can optionally supply a password to make it harder // to calculate the corresponding numeric ID

for ($n = 0; $n<strlen($index); $n++) {
$i[] = substr( $index,$n,1);
}

$passhash = hash('sha256',$passKey);
$passhash = (strlen($passhash) < strlen($index))
? hash('sha512',$passKey)
: $passhash;

for ($n=0; $n < strlen($index); $n++) {
$p[] = substr($passhash,1);
}

array_multisort($p,SORT_DESC,$i);
$index = implode($i);
}

$base = strlen($index);

if ($to_num) {
// Digital number < 0) {
$out -= pow($base,$pad_up);
}
}
$out = sprintf('%F',$out);
$out = substr($out,strpos($out,'.'));
} else {
// Digital number -->> alphabet letter code
if (is_numeric($pad_up)) {
$pad_up--;
if ($pad_up > 0) {
$in += pow($base,$pad_up);
}
}

$out = "";
for ($t = floor(log($in,$base)); $t >= 0; $t--) {
$bcp = bcpow($base,$t);
$a = floor($in / $bcp) % $base;
$out = $out . substr($index,$a,1);
$in = $in - ($a * $bcp);
}
$out = strrev($out); // reverse
}

return $out;
}

执行结果将被返回“fE2XnNGpF”，我们可以把它认为是加密，进行反解密则