increment alpha numerically values - php

Question

Like the title suggests I need to do something like so...
$i++;//we all know this.
$value = 'a';
increment($value);// i need this functionality
//output
string [ b ]
///here are some more samples, to help you understand...
increment('b'); //output// c
increment('z'); //output// A [capital A not fussy but would be good :) ]
increment('9'); //output// a1
increment('a1'); //output// a2
increment('aa1'); //output// aa2
and so on...
UPDATE
well lets say I use numeric values
$id++;
I would end up with a massive number eventuall 1310743942525;
which can take alot more space than say `ab34c9" im trying to save length of characters to save on db ...

Answer 1

You try to treat it as a base 62 number:
http://www.pgregg.com/projects/php/base_conversion/base_conversion.php
with source code at
http://www.pgregg.com/projects/php/base_conversion/base_conversion.inc.phps
convert it to decimal, increment, and convert it back to base 62
UPDATE
From how I read the code, you could have a workflow like this:
$value = 'ab8Zb';
$value_base10 = base_base2dec($value, 62);
$value_base10++;
$value = base_dec2base($value_base10, 62); // should be 'ab8Zc'

Answer 2

If all you are trying to do is save database space, consider this.
In MySQL you can have a field with a type UNSIGNED BIGINT. The maximum size of this field is 18446744073709551615 and the storage space is only 8 bytes.
If you were to convert this number (1.844 x 10^19) to base-62, it would be represented as LygHa16AHYF. You would need a CHAR(11) (11 bytes) or a VARCHAR(11) (12 bytes) in order to store the converted number.
If you used VARCHAR for the field type, smaller numbers would take less space, but for the larger numbers it actually takes more. 8 bytes for a huge number is pretty minimal anyway. I would save the effort and just make the DB field a UNSIGNED BIGINT.

Answer 3

You can use ascii codes of each letter. This is just a simple example that will show you the idea, ofcourse it need a lot of modyfications if you want to increment 'aa1' into 'aa2' but impossible is nothig ;P You will just need to write few conditions.
function increment($value)
{
if(strlen($value)>1)
return false;
$asciiCode = ord($value);
return chr($asciiCode + 1);
}
http://www.asciitable.com/ - ASCII codes table :)