How to generate random numeric string for a custom post type?

I have this PHP code to generate a random numeric string:

function generateRandomString($length = 12)
{
    global $generatedStrings;
    $characters = '0123456789';
    $randomString = '';
    for ($i = 0; $i < $length; $i++) {
        $randomString .= $characters[rand(0, strlen($characters) - 1)];
    }
    if (isset($generatedStrings[$randomString])) {
        $randomString = generateRandomString($length);
    }
    $generatedStrings[$randomString] = $randomString;
    return $randomString;
}

$generatedStrings = array();

foreach(range(1, 100000) as $num) {
    echo "\n".$num."\t : ".generateRandomString();
}

I was wondering if anyone could help figure out how to integrate this code with WordPress to auto-generate strings as slugs for a custom post type.

Any guidance you can provide is appreciated!