Convert MD5 to base62 for URL

Question

I have a script to convert to base 62 (A-Za-z0-9) but how do I get a number out of MD5?

I have read in many places that because the number from an MD5 is bigger than

Answer 1

You can do something like this,

$hash = md5("The data to be hashed", true);
$ints = unpack("L*num", $hash);

$hash_str = base62($ints['num1']) . base62($ints['num2']) . base62($ints['num3']) . base62($ints['num4'])

Answer 2

As of PHP 5.3.2, GMP supports bases up to 62 (was previously only 36), so brianreavis's suggestion was very close. I think the simplest answer to your question is thus:

function base62hash($source, $chars = 22) {
  return substr(gmp_strval(gmp_init(md5($source), 16), 62), 0, $chars);
}

Converting from base-16 to base-62 obviously has space benefits. A normal 128-bit MD5 hash is 32 chars in hex, but in base-62 it's only 22. If you're storing the hashes in a database, you can convert them to raw binary and save even more space (16 bytes for an MD5).

Since the resulting hash is just a string representation, you can just use substr if you only want a bit of it (as the function does).

Answer 3

Here is an open-source Java library that converts MD5 strings to Base62 strings https://github.com/inder123/base62

Md5ToBase62.toBase62("9e107d9d372bb6826bd81d3542a419d6") ==> cbIKGiMVkLFTeenAa5kgO4

Md5ToBase62.fromBase62("4KfZYA1udiGCjCEFC0l") ==> 0000bdd3bb56865852a632deadbc62fc

The conversion is two-way, so you will get the original md5 back if you convert it back to md5:

Md5ToBase62.fromBase62(Md5ToBase62.toBase62("9e107d9d372bb6826bd81d3542a419d6")) ==> 9e107d9d372bb6826bd81d3542a419d6

Md5ToBase62.toBase62(Md5ToBase62.fromBase62("cbIKGiMVkLFTeenAa5kgO4")) . ==> cbIKGiMVkLFTeenAa5kgO4

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