how to update array in laravel 5?

thanks for your help Mr. pyramid. here is the code:

public function update(Request $request, $id)
{

    $invoice = Invoice::findOrFail($id);

    $invoice->invoice_no = $request->invoice_no;
    $invoice->client = $request->client;
    $invoice->title = $request->title;
    $invoice->client_address = $request->client_address;
    $invoice->invoice_date = $request->invoice_date;
    $invoice->due_date = $request->due_date;
    $invoice->subtotal = $request->subtotal;
    $invoice->grandtotal = $request->grandtotal;

    $invoice->save();

    $products = $request->all();


      $name = $products['name'];
      $price = $products['price'];
      $qty = $products['qty'];
      $total = $products['total'];

     foreach( $name as $key => $n) {

        $invoice->products()->update([ 

             //=> $invoice->id,
            'name' => $name[$key],
            'price' => $price[$key],
            'qty' => $qty[$key],
            'total' => $total[$key]
        ]);
     } 




    Session::flash('success', 'Invoice Updated');

    return redirect()->route('invoices');

}

with this exactly code I can create and works fine but if i use to update it won't allow me.

database

Schema::create('invoices', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('invoice_no');
        $table->date('invoice_date');
        $table->date('due_date');
        $table->string('title');
        $table->string('client');
        $table->string('client_address');
        $table->decimal('subtotal');
        $table->decimal('grandtotal');
        $table->timestamps();
    });

products

Schema::create('products', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('invoice_id')->unsigned();
        $table->string('name');
        $table->string('qty');
        $table->string('price');
        $table->string('total');
        $table->timestamps();
    });

relationship

class Invoice extends Model {
protected $fillable =['client','client_address','title','invoice_no','invoice_date','due_date','discount', 'subtotal','grandtotal'];



public function products(){

    return $this->hasMany('App\Product', 'invoice_id');
}

}

class Product extends Model
{

protected $casts = [
    'name' => 'array',
    'price' => 'array',
    'qty' => 'array',
    'total' => 'array'
];
protected $fillable = ['invoice_id','price','qty','total','name'];


public function invoice(){

    return $this->belongsTo('App\Invoice');

}
}

thanks

I still have some doubts but I found something which I think can help you.

$invoice->products()->update($request->all());