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Question

Is there any way to hash a string, and un-hash it later?

For example, I want to hash an email address to make a unique link, and retrieve the email address when the link is visited.

It's more about obfuscation than hashing, as you can see.

Answer 1

You cannot hash and unhash a string but can use base64_encode and base64_decode to do a similar thing:

<?php
$str = 'This is an encoded string';
echo base64_encode($str);
?>

The above example will output:

VGhpcyBpcyBhbiBlbmNvZGVkIHN0cmluZw==

You can decode it:

<?php
$str = 'VGhpcyBpcyBhbiBlbmNvZGVkIHN0cmluZw==';
echo base64_decode($str);
?>

The above example will output:

This is an encoded string

As in the PHP.net manual:

http://php.net/manual/en/function.base64-encode.php

http://php.net/manual/en/function.base64-decode.php