Call to a member function store() on null (PostsController) - php

Question

I'm trying to save in database some elements and a photo with a form, I've added the "enctype="multipart/form-data" on the form and I've executed the command "php artisan storage:link", but when I click on Upload button, Laravel returns me this error: "Call to a member function store() on null" on file PostsController
Here is my file PostsController.php
<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\DB;
use App\Post;
class PostsController extends Controller
{
public function submitpost(Request $req)
{
$posttitle = $req->input('posttitle');
$postauthor = $req->input('postauthor');
$postcontent = $req->input('postcontent');
$img = $req->input('img')->store('public/img');
$dati = compact('posttitle', 'postauthor', 'postcontent', 'img');
$b = new Post();
$b->posttitle = $posttitle;
$b->postauthor = $postauthor;
$b->postcontent = $postcontent;
$b->img = $img;
$b->save();
$posts = Post::all();
return view('blog', compact('posts'));
}
}
This is my view file addpost.blade.php
<main class="main-content">
<div class="container-fluid photos">
<div class="row justify-content-center">
<div class="col-md-6 pt-4" data-aos="fade-up">
<h2 class="text-white mb-4">Create a new post</h2>
<div class="row">
<div class="col-md-12">
<div class="row">
<div class="col-md-12">
<form action="{{route('submitpost')}}" enctype="multipart/form-data" method="post">
#csrf
<div class="row form-group">
<div class="col-md-12">
<label class="text-white" for="subject">Post Title</label>
<input type="subject" name="posttitle" id="subject" placeholder="Give a title to the post" class="form-control">
</div>
</div>
<div class="row form-group">
<div class="col-md-12">
<input type="subject" readonly hidden name="postauthor" id="subject" value="{{Auth::user()->name}}" class="form-control">
</div>
</div>
<div class="row form-group mb-5">
<div class="col-md-12">
<label class="text-white" for="message">Content of post</label>
<textarea name="postcontent" id="message" cols="30" rows="7" class="form-control" placeholder="Write your post here"></textarea>
</div>
</div>
<div class="row form-group">
<div class="col-md-12">
<input type="file" name="img" value="{{old('img')}}" placeholder="Image" value="">
</div>
</div>
<div class="row form-group">
<div class="col-md-12">
<input type="submit" value="Create Post" class="btn btn-primary btn-md text-white">
</div>
</div>
</form>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</main>
This is my Route in web.php
Route::post('/addpost/submitpost', 'PostsController#submitpost')->name('submitpost');
And this is my model Post.php
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Post extends Model
{
protected $fillable = [
'posttitle',
'postauthor',
'postcontent',
'img',
];
protected $table = 'posts';
}

Answer 1

As you can see in the documentation, uploaded files can be accessed using the file() method.
Try updating this:
$img = $req->input('img')->store('public/img');
To this:
$path = $req->file('img')->store('public/img');
^^^^^^^^^^
Also, you can confirm if the request actually has the file in its payload checking if the file exists, to avoid exceptions:
if ($req->hasFile('img')) {
$path = $req->file('img')->store('public/img');
}
This and more useful methods, can be seen in the File Uploads section of the docs.