Recuperando o ID usando Eloquent do Laravel

Post-2.php

<?php

class Post extends Eloquent
{
    public $incrementing = false;
}

Post.php

<?php

class Post extends Eloquent
{
    
}

PostsController-2.php

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Http\Controllers\Controller;

use App\Post;

class PostsController extends Controller
{
    public function index(){
        $post = new Post;
        $post->id = 123; // definimos o ID manualmente
        $post->title = "Primeiro Post";
        $post->body = "Texto do primeiro post";
        $post->save();
        
        return $post->id; // isso agora ira imprimir 0
    }
}

PostsController.php

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Http\Controllers\Controller;

use App\Post;

class PostsController extends Controller
{
    public function index(){
        $post = new Post;
        $post->title = "Primeiro Post";
        $post->body = "Texto do primeiro post";
        $post->save();
        
        return $post->id;
    }
}