- substr: documentation ( source)
- str_replace: documentation ( source)
- ceil: documentation ( source)
- base64_encode: documentation ( source)
<?php
$n = 12;
echo base64_encode(strong_random_bytes(intval(ceil($n * 3 / 4))));
echo substr(str_replace(['/', '+', '='], ['', '', ''], base64_encode(strong_random_bytes($n))), 0, $n);