How to convert a String to a unique INTEGER in php

The amount of information a PHP integer may store is limited. The amount of information you can store in a string is not (at least if the string isn't unreasonably long.)

Thus you would need to compress your arbitrary-length string to an non-arbitrary-length integer. This is impossible without data loss.

You may use a hashing algorithm, but hashing algorithms may always have collisions. Especially if you want to hash a string to an integer the collision probability is pretty high - integers can store only very little data.

Thus you shall either stick with the email or use an auto incrementing integer field.

Try the binhex function

from the above site:

<?php
$str = "Hello world!";
echo bin2hex($str) . "<br />";
echo pack("H*",bin2hex($str)) . "<br />";
?>

outputs

48656c6c6f20776f726c6421
Hello world!

Why not just have an auto-increment ID field on the database?