Update an additional user meta field with a string

Question

I have created a WordPress website. In the user section I have created an additional attribute called "Token" meta field. Every time a new user is created or a user logs in and is validated, I would like to update this Token attribute with a random string. I would really appreciate some help in going about doing this. Thank you. This is my code so far during a user log in where randomString is the variable storing the random string.

         function login_user($request) {
          $length = 10;
          $characters = 
      '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
          $charactersLength = strlen($characters);
          $randomString = '';
        for ($i = 0; $i < $length; $i++) {
          $randomString .= $characters[rand(0, $charactersLength - 1)];
        }
          $params = $request->get_params();
          $email = $params['email'];
          $pass = $params['password'];
          $user = get_user_by('email', $email);
             $user_id = $user->ID;
            if ( $user && wp_check_password( $pass, $user->data->user_pass, $user->ID) ){
                return $randomString;
                return "true";
             }
            else {
                 return "false";
             } 

Answer 1

You're almost there.

You can use this to update user meta: https://codex.wordpress.org/Function_Reference/update_user_meta.

Create your custom field using ACF (Advanced Custom Fields).