#1

bin2hex(random_bytes(16));

#2

function random_str(

    $length = 32,

    $chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'

) {

    $rand_str = '';

    $max = mb_strlen($chars) - 1;

    for ($i = 0; $i < $length; $i++)

    {

        $rand_index = random_int(0, $max);

        $rand_str .= $chars[$rand_index];

    }

    return $rand_str;

}