Foreign Key doesn't have a default value

sorry user_id, but I'm a bit confused I'm not sure how to insert the value of the foreign id to the new data!

$guest = new Guest();

... (all other code here same)

$guest->guest_id = 1; (This should be the ID of the guest)

$guest->save();

Thank you but, this is inserting the guest_id to the controller manually! How can I pass it automatically to match the entered data, what I'm trying to say is if I want add new row inside the booking_guest_room that relates to a user inside the customer_info table what should so that once I insert the data inside the booking_guest_room it creates automatically a new id inside the customer_info?

Need more info, perhaps try paste the code here in the forum and use markdown to highlight it

Sorry I can't describe what I really need to do good it feels like the steps are not organized in my brain, here is the code here is model for booking_guest_info table https://pasteboard.co/JOU6MbQ.png here is my model for customer_info table https://pasteboard.co/JOU7Gjr.png here is my controller for booking_guest_info https://pasteboard.co/JOU86Ky.png also this is the guest_info controlloer https://pasteboard.co/JOU8rlQ.png

You are welcome, one step after the other

First, it's better (easy to read) to share code here, put it between 3 `

first code :

...
blabla

second one

blabla2

This is the GuestRoom controller which contains the user room info

`public function store(Request $request) {

    $room = new Room;
    $room->room_nums = $request->room_num;
    $room->room_type = $request->room_type;
    $room->adults = $request->adults;
    $room->child = $request->child;
    
    dd($room->id);
    $room->save();
    return redirect('/guest');
    
}

This is the guest_info controller

    {
        $guest = new Guest;
        $guest->guest_name = $request->name;
        $guest->nationality = $request->nationality;
        $guest->email = $request->email;
        $guest->mobile_num = $request->mobile;
        $guest->save();
        return redirect('/res');
    }```

This is the room info model

class Room extends Model
{
    use HasFactory;
    public $timestamps = false;
    protected $table = 'booking_guest_room';
    protected $fillable = ['user_id', 'id'];

    public function rooms(){
        return $this->hasMany(Room::class, 'user_id');
    }
}

This is the guest info model

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Guest extends Model
{
    
    use HasFactory;
    protected $table = 'customer_info';
    public $timestamps = false;
    


   
}

This is the blade where I enter the room info and submit it

                <div class="step">
                    <form  method="post" action="{{route('res.store')}}">            
                        @method('POST')
                        @csrf
                    <div class="row">
                        <div class="col-md-12 col-sm-12">
                            <div class="form-group">
                                <table class="table table-striped table-inverse table-responsive form" >
                                    <thead class="thead-inverse">
                                        <tr class="w-5">
                                            <!-- <th>Room NO.</th> -->
                                            <th>نوع الغرفة</th>
                                            <th>الكبار</th>
                                            <th>الاطفال</th>
                                            <!-- <th>Child Ages</th> -->
                                            <th>احذف الغرفة</th>
                                        </tr>
                                        </thead>
                                    <tbody id='myTable'>
                                    {{-- here goes the table info --}}
                                    </tbody>
                                    <button class="add rounded btn btn-danger " type="button">اضف الغرفة</button>
                                    <!-- <button class="remove">Remove Room</button> -->
                                    <input type="number" class="numbers" value="" name="room_num" min="0" placeholder="عدد الغرف">
                                </table>
                            </div>
                        </div>
                        
                    </div>
                    <input type="number" name="user_id" id="" value="{{$room->id}}">

                    <hr>

                    <button class="btn btn-info" >Book now</button>

Shouldn't the rooms have many guests. And the room belongs to guest

Yes exactly but I don't how to translate this to the code

how to do it if use resources controller like Route::resource('guest', GuestController::class);

With a resource controller you'll have access to the 2 (or more) tables.

I really suggest you (re)read the docs, follow this course

https://laracasts.com/series/laravel-6-from-scratch

and maybe before https://laracasts.com/skills/laravel

and do a first simple example.