Implement PHP code that turns the digital ID to letter Id

Alphaid (12354);  //converts numbers to letters.  
  alphaid (' Ppqxn7cof ', true);//will convert the letter ID to the corresponding number.  
  Alphaid (12354,false,6);//Specifies that the length of the generated letter ID is 6.

Source:

<?php/** * Translates a number to a short alhanumeric version * * Translated no number up to 900719925474099 2 * to a shorter version in letters e.g.: * 9007199254740989--> PPQXN7COF * * specifiying the second argument True, it would * translate back e.g: * PPQXN7COF--> 9007199254740989 * * This function is based on Any2dec &am 
 p;& Dec2any by * fragmer[at]mail[dot]ru * see:http://nl3.php.net/manual/en/function.base-convert.php#52450 * * If you are want the alphaid to being at least 3-long, use the * $pad _up = 3 Argument * * In most cases this is bet 
 ter than totally random ID generators * Because this can easily avoid ID ' s. 
 * For example if your correlate the Alpha ID to a auto incrementing ID * in your database, and you are done.  * * The reverse is done because it makes it slightly more cryptic, * but it also makes it easier to spread of IDs In different * directories on your filesystem. Example: * $part 1= substr ($alpha _id,0,1); 
 * $part 2 = substr ($alpha _id,1,1); 
 * $part 3 = substr ($alpha _id,2,strlen ($alpha _id)); * $destindir = "/". $part 1. " /". $part 2." 
 /". $part 3; *//By reversing, directories are more evenly spread out. The *///directories already occupy main levels * More info on limitation: *-Http://blade.nagaokau  
 t.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/165372 * * If you are really need this for bigger numbers your probably to look * at things like:http://theserverpages.com/php/manual/en/ref.bc.php * or:http://theserverpages.com/php/manual/en/re f.gmp.php * But I haven ' t really dugg into this. 
 If you are have more info on those * matters feel free to leave a comment. * @author Kevin van Zonneveld <kevin@vanzonneveld.net> @author Simon Franz * @author deadfish * @copy Right 2008 Kevin van Zonneveld (http://kevin.vanzonneveld.net) * @license Http://www.opensource.org/licenses/bsd-licen se.php New BSD Licence * @version SVn:release: $Id: alphaID.inc.php 344 2009-06-10 17:43:59z Kevin $ * @link http://kevin.vanzonneveld.net/* * @pa  Ram mixed $in String or long input to translate * @param a Boolean $to _num reverses translation when True * @param Mixed $pad _up number or Boolean padds the result up to a specified length * @param string $passKey supplying a pass Word makes it harder to calculate the original ID * @return mixed string or long/function Alphaid ($in, $to _num = False, $pad _up = false, $passKey = null) {$index = "abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxy  
  Z ";  if ($passKey!== null) {//Although this function ' s purpose's to just make the//ID Short-and  Secure,//With this patch by Simon Franz (http://blog.snaky.org/)//Your can optionally supply a password to   
      Make it harder/calculate the corresponding numeric ID for ($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, $n, 1);  
    //unity3d script: http://www.unitymanual.com//http://www.bianceng.cn Array_multisort ($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; }

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