How to generate unique random value for each user in laravel and add it to database

Question

I am developing a event organization website. Here when the user registers for an event he will be given a unique random number(10 digit), which we use to generate a barcode

Answer 1

I made something like this

/**
 * Generate unique shipment ID
 * 
 * @param int $length
 * 
 * @return string
 */ 
function generateShipmentId($length)
{
    $number = '';

    do {
        for ($i=$length; $i--; $i>0) {
            $number .= mt_rand(0,9);
        }
    } while ( !empty(DB::table('shipments')->where('id', $number)->first(['id'])) );

    return $number;
}