PHP实现把数字ID转字母ID

 alphaID(12354）；  //会将数字转换为字母。   alphaID('PpQXn7COf',true）；//会将字母ID转换为对应的数字。   alphaID(12354,false,6）；//指定生成字母ID的长度为6.

源码：

<?php/** * Translates a number to a short alhanumeric version * * Translated any number up to 9007199254740992 * to a shorter version in letters e.g.: * 9007199254740989 --> PpQXn7COf * * specifiying the second argument true, it will * translate back e.g.: * PpQXn7COf --> 9007199254740989 * * this function is based on any2dec && dec2any by * fragmer[at]mail[dot]ru * see: http://nl3.php.net/manual/en/function.base-convert.php#52450 * * If you want the alphaID to be at least 3 letter long, use the * $pad_up = 3 argument * * In most cases this is better than totally random ID generators * because this can easily avoid duplicate ID's. * For example if you correlate the alpha ID to an auto incrementing ID * in your database, you're done. * * The reverse is done because it makes it slightly more cryptic, * but it also makes it easier to spread lots of IDs in different * directories on your filesystem. Example: * $part1 = substr($alpha_id,0,1); * $part2 = substr($alpha_id,1,1); * $part3 = substr($alpha_id,2,strlen($alpha_id)); * $destindir = "/".$part1."/".$part2."/".$part3; * // by reversing, directories are more evenly spread out. The * // first 26 directories already occupy 26 main levels * * more info on limitation: * - http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/165372 * * if you really need this for bigger numbers you probably have to look * at things like: http://theserverpages.com/php/manual/en/ref.bc.php * or: http://theserverpages.com/php/manual/en/ref.gmp.php * but I haven't really dugg into this. If you have more info on those * matters feel free to leave a comment. * * @author  Kevin van Zonneveld <[e-mail]> * @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, $n ,1);    }    //unity3d脚本：http://www.unitymanual.com    array_multisort($p,  SORT_DESC, $i);    $index = implode($i);  }  $base  = strlen($index);  if ($to_num) {    // Digital number  <<--  alphabet letter code    $in  = strrev($in);    $out = 0;    $len = strlen($in) - 1;    for ($t = 0; $t <= $len; $t++) {      $bcpow = bcpow($base, $len - $t);      $out   = $out + strpos($index, substr($in, $t, 1)) * $bcpow;    }    if (is_numeric($pad_up)) {      $pad_up--;      if ($pad_up > 0) {        $out -= pow($base, $pad_up);      }    }    $out = sprintf('%F', $out);    $out = substr($out, 0, 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;}