Base36 Encoding for Tiny URLs With PHP

While adding permalink and Twitter support to Onyx last week, I realized that PHP can easily convert a number between two arbitrary bases using its built in base_convert function.  This was crucial for me because it meant that I could quickly generate a base-36 encoded string from a standard base-10 number:

$tiny = base_convert($key, 10, 36);

As Wikipedia explains, "...the choice of 36 is convenient in that the digits can be represented using the Arabic numerals 0-9 and the Latin letters A-Z.  Base 36 is therefore the most compact case-insensitive alphanumeric numeral system using ASCII characters...".  Not to mention, it's the highest radix most languages support by default.

I built Onyx to maintain a list of files (as inode's) in a MySQL database table.  Luckily, the inode's are stored in this table as auto incrementing BIGINT(20)'s, which are of course, base-10 encoded numbers:

CREATE TABLE files (

  f_inode BIGINT(20) NOT NULL AUTO_INCREMENT,
  ...

  INDEX inode_index ( f_inode ),
  PRIMARY KEY ( f_inode ),
  ...

) TYPE=InnoDB;

Base-36 encoding my inode's is key because this means that I can easily, for example, convert base-10 inode 3,032 into "2c8" base-36 for a tiny URL.  From there, it's simply a matter of using the base-36 encoded string in a tiny/shortened permalink URL to refer to the correct file/inode on Onyx.  Yes, this is a poor example because I'm only saving 1 character in a supposedly shorter URL ("3032" vs "2c8").  However, this makes a lot more sense with larger base-10 numbers like 105,621,983 which condenses nicely into "1qvufz" base-36.  Personally, I'd rather see /1qvufz on the end of a "tiny" URL than /105621983.

Enjoy.