PHP base64 encoding custom alphabet

Question

I try to use base64_encode() and base64_decode() but with custom alphabet. Default alphabet is:

"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

say I want to use:

"ZYXWVUTSRQPONMLKJIHGFEDCBAzyxwvutsrqponmlkjihgfedcba9876543210+/" 

found a class on internet but doesn't work as expected. Any idea on how to achieve this as simple as possible?

Answer 1

Ultra easy, strtr can do this out of the box:

$default = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
$custom  = "ZYXWVUTSRQPONMLKJIHGFEDCBAzyxwvutsrqponmlkjihgfedcba9876543210+/";

$encoded = strtr(base64_encode($input), $default, $custom);

Answer 2

In addition to the custom encoding defined above, to decode with a custom alphabet, you can do the following:

    $custom = 'ZYXWVUTSRQPONMLKJIHGFEDCBAzyxwvutsrqponmlkjihgfedcba9876543210+/';
    $default = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
    $decoded = base64_decode(strtr($input, $custom, $default));