How to find next numeric/alpha character

[dlebowski]

What I am trying to do is find out what the next value would be if I am using a combination of alpha and numeric characters.  For example, if I have the number 1.  The next value would be 1a, next would be 1b, etc.  When you get to 1z, it would then go 1aa, 1ab, 1ac, etc....

 

Does anyone know how I would accomplish this?  Thank you in advance!

 

Ryan

[Mchl]

<?php
function nextNumber($previous) {
  if(is_numeric($previous)) {
    $next = $previous.'a';
  } else  if(substr($previous,-1) == 'z') {
    $next = substr($previous,0,-1).'aa';
  } else {
    $lastChr = substr($previous,-1);
    $next = substr($previous,0,-1).++$lastChr;
  }
  return $next;
}

echo nextNumber('1');   // 1a
echo nextNumber('1a');   // 1b
echo nextNumber('1z');   // 1aa
echo nextNumber('1aa');   // 1ab
echo nextNumber('1ab');   // 1ac

[jcbones]

And to use Mchl's function in a loop to show multiple numbers.

$result = 1;
for($i = 0; $i < 100; $i++) {
$result = nextNumber($result);
echo $result . '<br />';
}