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convert decimals 2 alphabet

convertDec2Alpha.php

Convert a decimal to an alphabetical (alphabet based) string

Added: 2006-05-05 18:41:23
Last update: 2007-09-30 17:20:32

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<?
/******

* You may use and/or modify this script as long as you:

* 1. Keep my name & webpage mentioned

* 2. Don't use it for commercial purposes

*

* If you want to use this script without complying to the rules above, please contact me first at: marty@excudo.net

* 

* Author: Martijn Korse

* Website: http://devshed.excudo.net

*

* Date:  2006-05-05 18:41:23

***/



 /*****

  * Converts any integer ($int) into an alphabetic range of $length length

  * p.a.: 1 => AA, 2 => AB, 27 => BA

  ***/

function convDec2Alpha($int, $length=2)

{

   $int = $int - 1;            // minus one, cuz A is in position 0 in the alphabet array

   $alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";   // the alphabet

   $a = strlen($alphabet);            // the length of the alphabet

   $maxPosibilities = pow($a, $length);      // maximum posibilities, given the the ($)length of the output and the length of the alphabet



   $restValue = $int % $maxPosibilities;      // if $int exceeds the maxPosibilities, we start counting again from scrats. For this, we use the modulus



   $output = "";               // initiating output variable

   $x = $length - 1;            

    /***

     * We're gonna loop $length times, but since we end at 0 we start at $length -1.

     * This is done on purpose, because x is gonna be used as a 'power of'

     */

   while ($x >= 0)

   {

       // calculating the position (index) of the new character)

      $thisCharIndex = floor($restValue / pow($a, $x));

      $thisChar = $alphabet{$thisCharIndex};



      $restValue = $restValue - (pow($a, $x) * $thisCharIndex);



       // adding character to the output

      $output .= $thisChar;

      $x--;

   }

   return $output;               // return output

}

 /*****

  * Converts any alphabetic range of characters into an integer ($int) value

  * p.a.: AA => 1, AC => 3, BA => 27

  ***/

function convAlpha2Dec($str)

{

   $str = strtoupper($str);

   $alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";   // the alphabet

   $maxI = (strlen($str) - 1);

   $int = 0;

   for ($i=0; $i<=$maxI; $i++)

   {

      $thisPos = strpos($alphabet, $str{$i});

      if ($i < $maxI)

      {

         $int += pow(strlen($alphabet), ($maxI - $i)) * $thisPos;

      }

      else   /* $i == $maxI */

      {

         $int += ($thisPos + 1);

      }

   }

   return $int;

}

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