// Created on savesnippets.com · https://savesnippets.com/0fWqIbY5QWx9jl
<?php
function readableToken(int $len = 8): string {
    // Crockford-style alphabet — no 0, O, 1, l, I, U
    $alpha    = 'ABCDEFGHJKMNPQRSTVWXYZ23456789';
    $alphaLen = strlen($alpha);
    $out      = '';
    for ($i = 0; $i < $len; $i++) {
        // Rejection sampling for uniform distribution.
        do { $b = ord(random_bytes(1)); } while ($b >= intdiv(256, $alphaLen) * $alphaLen);
        $out .= $alpha[$b % $alphaLen];
    }
    return $out;
}

echo readableToken(6);   // e.g. "K7TQ4N"
echo readableToken(12);  // e.g. "X3RJ8H2BVQ7K"