Get id of inserted row and use for the next query?

Im currently pushing myself to do little projects for myself that are well out of my depth but learning a heck of a lot quickly. But there are a few things i have no idea about or if its even possible...

What i'm trying to do is sync a table with another (ish).

What it does is to Grab all the Reservations and create a Event from those reservations in an event calendar (Wordpress).

The problem I'm getting is that when I save a reservation it adds it to the events table but it also needs a post to link to it.

So what im looking to do is:

When it syncs -> get all the bookings and go through each one to see if its in the events table or not.

Then the ones that aren't, I want it to insert the data as below:

    $booking = new Event(array(
                'post_id' => 5281,
                'StartDate' => date('Y-m-d', strtotime($booking->check_in)),
                'EndDate' => date('Y-m-d', strtotime($booking->check_in)),
                'StartTime' => date('G:i:00', strtotime($booking->start_hour)),
                'FinishTime' => date('G:i:00', strtotime($booking->end_hour)),
                'event_occurrence' => 0,
            ));
            $booking->save();     

This then creates the new event. As you can see the 'post_id' is hardcoded to grab a pre made post. But what i noticed is that it doesn't work correctly, so to get around this I wanted to make a new post before the booking and grab the id of the new post and insert it in post_id.

Im really not sure if this is possible or not or how to even go about it.

Heres the layout of the db and the code i have.

// Posts
        // =====
        // ID
        // post_author
        // post_date = NOW()
        // post_date_gmt
        // post_content
        // post_title
        // post_status = publish
        // comment_status
        // ping_status
        // post_name = url slug
        // post_type = event
        // guid =?post_type=event&p=4024 (p=id)

        // Reservations
        // ==========
        // id 
        // calendar_id
        // woo_order_id
        // check_in (date)
        // check_out (date)
        // start_hour
        // end_hour
        
    // Events
        // ======
        // event_id = created at time
        // post_id = 4024
        // StartDate = check_in
        // EndDate = check_out
        // StartTime = start_hour
        // FinishTime = end_hour

And the code:

// Create the bookings
        $bookings = Booking::all();

        foreach($bookings as $booking) { 
            $event = new Post(array(
                'post_author' => 8,
                'post_date' => NOW(),
                'post_date_gmt' => NOW(),
                'post_content' => 'Reserved Booking',
                'post_title' => 'Reserved Booking',
                'post_status' => 'publish',
                'comment_status' => 'closed',
                'ping_status' => 'closed',
                'post_name' => 'reserved' . str_random(3),
                'post_type' => 'event'
            ));
            $event->save();

            $booking = new Event(array(
                'post_id' => 5281,
                'StartDate' => date('Y-m-d', strtotime($booking->check_in)),
                'EndDate' => date('Y-m-d', strtotime($booking->check_in)),
                'StartTime' => date('G:i:00', strtotime($booking->start_hour)),
                'FinishTime' => date('G:i:00', strtotime($booking->end_hour)),
                'event_occurrence' => 0,
            ));

            $booking->save();  
         
        }

        $count = $booking->count();  

        return redirect(action('EventsController@index'))
                ->with('status', $count . ' entries have been added to the database!');
    }

Many thanks