Represent MD5 hash as an integer

Question

In my user database table, I take the MD5 hash of the email address of a user as the id.

Example: email(example@example.org) = id(d41d8cd98f00b204e9800998ecf8427e)

Answer 1

For a 32-bit condensation, a simple solution could be made by selecting 4 hex pairs (8 characters) of the MD5 hash, where each pair represents one byte, and then converting that with intval().

For an unsigned 32-bit Int:

$inthash = intval(substr(md5($str), 0, 8), 16);

For the positive value only of a signed 32-bit Int:

$inthash = intval(substr(md5($str), 0, 8), 16) >> 1;

This will likely only work for values up to 64-bit (8 bytes or 16 characters) for most modern systems as noted in the docs.

On a system that can accommodate 64-bit Ints, a splitting strategy that consumes the entire 128-bit MD5 hash as 2 Ints might look like:

$hash = md5($str);
$inthash1 = intval(substr($hash, 0, 16), 16);
$inthash2 = intval(substr($hash, 16, 16), 16);