PHP Laravel save() is not updating record - php

Question

I am a beginner in laravel. I was updating records but I can't figure out what is wrong with my $student->save();
My controller code is as follows
<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
use App\Models\Student;
use PHPUnit\Framework\MockObject\Builder\Stub;
class HomeController extends Controller
{
public function read() {
$students = Student::all();
return view('read',['Students'=>$students]);
}
public function insert() {
return view('insert');
}
public function insertPost(Request $req) {
$student=new Student();
$student->Name = $req->input('name');
$student->Marks = $req->input('marks');
$student->save();
return redirect('/');
}
public function update($id) {
$student = Student::find($id);
return view('update',['Student'=>$student]);
}
public function delete($id) {
$student = Student::find($id);
$student->delete();
}
public function updatePost(Request $req) {
$student = Student::find($req->input('id'));
$student->Name=$req->input('name');
$student->Marks=$req->input('marks');
$student->save();
// Student::where('ID',$req->input('id'))
// ->update(['Name'=>$req->input('name'),
// 'Marks'=>$req->input('marks')]);
return redirect('/');
}
}
The Main main in updatePost(); is causing the records not updating
$student = Student::find($req->input('id'));
$student->Name=$req->input('name');
$student->Marks=$req->input('marks');
$student->save();
I changed the way of updating records to
Student::where('ID',$req->input('id'))
->update(['Name'=>$req->input('name'),
'Marks'=>$req->input('marks')]);
and it worked. But I wanted to know at which part I was making mistake in it.

Answer 1

You need to set your primary key to 'ID'
By default the primary key or PK name is 'id'
But in your code it changed to 'ID'
So you need to go to your User.php model class
and add this line
public $primaryKey = 'ID';

Answer 2

One thing you can try is using Laravel's update method. update will handle the save internally.
$student = Student::findOrFail($req->input('id')));
$student->update([
'Name' => $req->input('name'),
'Marks' => $req->input('marks'),
]);