function splitter($subject, $n, array $symbols) {
return implode(array_map(function ($part) use ($n, $symbols) {
if (strlen($part) === $n) {
$part .= $symbols[array_rand($symbols)];
}
return $part;
}, str_split($subject, $n)));
}
echo splitter('0000000000000000000000', rand(1, 3), [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]);