How to get the id of the current model in Laravel when saving
Stefan Bogdanescu
Founder & Senior Architect · 2026-06-29
# How to Get the Parent Model ID When Saving Child Models in Laravel
As developers working with relational data in frameworks like Laravel, managing foreign key relationships is fundamental. A very common scenario arises when you need to create a new record (like a `Comment`) that belongs to an existing parent record (like a `Project`). The challenge often lies in correctly passing that parent's ID from the front-end form submission back to the controller so Eloquent can establish the relationship properly during the save operation.
This post will walk you through the common pitfalls when dealing with nested data and provide robust, modern solutions for retrieving parent IDs when saving new models in a Laravel application.
## Understanding the Problem: The Missing Link
You are encountering an error like `Trying to get property of non-object` because you are attempting to access a relationship (e.g., `$comment->project_id`) on an object that either doesn't exist or hasn't been properly hydrated with the necessary data *before* the save operation occurs.
In your specific case, when saving a `Comment`, you need the ID of the related `Project`. If this ID isn't explicitly provided via the request, Laravel cannot automatically infer it through a simple relationship call unless the parent model is already loaded onto the request.
The core issue isn't just about getting the ID; it's about ensuring that the data sent from the form correctly maps to the foreign key column in your database table.
## Solution 1: The Eloquent and Request Approach (The Ideal Way)
The most robust way to handle this in Laravel is to rely on the `FormRequest` object to validate and retrieve all necessary input fields. This approach keeps your controller clean and leverages Laravel's built-in validation mechanisms, which is a core principle of building scalable applications, as emphasized by the principles found at [laravelcompany.com](https://laravelcompany.com).
Instead of trying to calculate relationships directly in the controller based on assumptions, you should explicitly ask for the foreign key.
### Step 1: Define the Request Rules
Ensure your `CommentsFormRequest` (or similar request) expects the `project_id`.
```php
// app/Http/Requests/CommentsFormRequest.php
public function authorize()
{
return true;
}
public function rules()
{
return [
'message' => 'required|string',
'project_id' => 'required|integer|exists:projects,id', // Crucial validation!
'user_id' => 'required|exists:users,id',
];
}
```
### Step 2: Retrieve the ID in the Controller
The `$request->input('project_id')` method is the cleanest way to access this data. This shifts the responsibility of fetching the ID from complex object navigation to simple input retrieval.
```php
// app/Http/Controllers/CommentController.php
use Illuminate\Http\Request;
public function store(CommentsFormRequest $request)
{
// 1. Retrieve the foreign key directly from the request