PHP把数字ID转字母ID

PHP把数字ID转字母ID

2014-08-09

    ID是网站中经常出现的，它一般是数字，但是我们发现现在的网站很多ID都是字母了,比如YouTube的视频播放页它的URL类似/watch?v=yzNjIBEdyww。 下面是一个生成字母ID的方法。
   使用示例：

    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, $n ,1);          }                 array_multisort($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;      }