Why does my random function always returns same number? [duplicate]

I have an ID system with PHP. It generates a 12 digit ID this way:

// create a 12 digit ID
function createTwelveId(){
  $digit_1 = rand(0, 9);

  $digit_2 = rand(0, 9);

  $digit_3 = rand(0, 9);

  $digit_4 = rand(0, 9);

  $digit_5 = rand(0, 9);

  $digit_6 = rand(0, 9);

  $digit_7 = rand(0, 9);

  $digit_8 = rand(0, 9);

  $digit_9 = rand(0, 9);

  $digit_10 = rand(0, 9);

  $digit_11 = rand(0, 9);

  $digit_12 = rand(0, 9);

  $pre_twelve_id = $digit_1 . $digit_2 . $digit_3 . $digit_4 . $digit_5 . $digit_6 . $digit_7 . $digit_8 . $digit_9 . $digit_10 . $digit_11 . $digit_12;

  return $pre_twelve_id;
}

When called, it is like this:

$comment_ID = createTwelveId();

And then it is inserted into my database this way:

//create comment
  $sentence = $connection->prepare("
    INSERT INTO comments (ID)
    VALUES (:ID)
");
$sentence->execute(array(
  ':ID' => $comment_ID
));

But every time I check the result on the database, it always inserts this:

004294967295

Please notice on this column I have Zerofill and Unsigned values on, that's why the int has 2 zeros at the beginning. And when I remove the Zerofill and Unsigned values, it inserts this:

2147483647

It always does this. Isn't it supposed to insert a random int into the database instead of those 2 numbers?

How can I stop this from happening and instead of those 2, insert the real random characters?