如何在Laravel上的app / Mail VeryfyMail.php上生成随机令牌？

working with Laravel 5.7 and I have VeryfyMail system. I need sending some random number to subject on email in app/Mail VeryfyMail.php file,

VeryfyMail.php

<?php

namespace App\Mail;

use Illuminate\Bus\Queueable;
use Illuminate\Mail\Mailable;
use Illuminate\Queue\SerializesModels;
use Illuminate\Contracts\Queue\ShouldQueue;

class VerifyMail extends Mailable
{
    use Queueable, SerializesModels;

    public $user;

    public function __construct($user)
    {
        $this->user = $user;
    }


    public function build()
    {
        //return $this->view('emails.verifyUser');
        return $this->subject('')->view('emails.verifyUser');
    }
}

how can I generate some ramdon number on above file subject?

Since you said you want he random token as the subject, just do:

Getting a random string (hex)

When creating tokens, you usually want something that's cryptographically secure to make it much harder for clever attackers to "guess" the tokens. Luckily, PHP introduced random_bytes() in PHP 7.

This will create a hexadecimal random token:

// Get some random bytes
$token = random_bytes(8);

// Since random_bytes() returns a string with all kinds of bytes, 
// it can't be presented "as is".
// We need to convert it to a better format. Let's use hex
$token = bin2hex($token)

// Now just add the variable as the subject
return $this->subject($token)->view('emails.verifyUser');

Getting a random number (integer)

If you rather want only numbers, we can use random_int() instead:

// Generate the token. Add the min and max value
$token = random_int(1000000, 9999999);

// Use it as the subject
return $this->subject($token)->view('emails.verifyUser');