encodeFunction.php

<?php	
function alphaID($in, $to_num = false, $pad_up = false, $pass_key = null)
	{
	  $out   =   '';
	  $index = 'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
	  $base  = strlen($index);

	  if ($pass_key !== null) {

	    for ($n = 0; $n < strlen($index); $n++) {
	      $i[] = substr($index, $n, 1);
	    }

	    $pass_hash = hash('sha256',$pass_key);
	    $pass_hash = (strlen($pass_hash) < strlen($index) ? hash('sha512', $pass_key) : $pass_hash);

	    for ($n = 0; $n < strlen($index); $n++) {
	      $p[] =  substr($pass_hash, $n, 1);
	    }

	    array_multisort($p, SORT_DESC, $i);
	    $index = implode($i);
	  }

	  if ($to_num) {
	    // Digital number  <<--  alphabet letter code
	    $len = strlen($in) - 1;

	    for ($t = $len; $t >= 0; $t--) {
	      $bcp = bcpow($base, $len - $t);
	      $out = $out + strpos($index, substr($in, $t, 1)) * $bcp;
	    }

	    if (is_numeric($pad_up)) {
	      $pad_up--;

	      if ($pad_up > 0) {
	        $out -= pow($base, $pad_up);
	      }
	    }
	  } else {
	    // Digital number  -->>  alphabet letter code
	    if (is_numeric($pad_up)) {
	      $pad_up--;

	      if ($pad_up > 0) {
	        $in += pow($base, $pad_up);
	      }
	    }

	    for ($t = ($in != 0 ? floor(log($in, $base)) : 0); $t >= 0; $t--) {
	      $bcp = bcpow($base, $t);
	      $a   = floor($in / $bcp) % $base;
	      $out = $out . substr($index, $a, 1);
	      $in  = $in - ($a * $bcp);
	    }
	  }
	  return $out;
	}