PHP實現把數字ID轉字母ID的方法

本文主要和大家分享PHP實現把數字ID轉字母ID的方法，希望能協助到大家。

alphaID(12354）；  //會將數字轉換為字母。  alphaID('PpQXn7COf',true）；//會將字母ID轉換為對應的數字。  alphaID(12354,false,6）；//指定產生字母ID的長度為6.

<?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 <kevin@vanzonneveld.net>  * @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;  }