Increase Quantity If Product don't Exists yet In Cart - php

Question

i want to be able to increase and decrease quantity item before submiting data to the cart
this is my increase and decrese methods they work fine already tested
public function decrease($id)
{
$user = Auth::user();
$panier = $user->panier;
foreach ($panier->produits as $produit) {
if ($produit->id == $id) {
$qt = $produit->pivot->quantite;
$qt--;
if ($qt == 0) {
$panier->produits()->detach($produit->id);
} else {
$panier->produits()->updateExistingPivot($produit->id, ['quantite' => $qt]);
}
}
}
return redirect()->back();
}
public function increase($id)
{
$user = Auth::user();
$panier = $user->panier;
foreach ($panier->produits as $produit) {
if ($produit->id == $id) {
$qt = $produit->pivot->quantite;
$qt++;
$panier->produits()->updateExistingPivot($produit->id, ['quantite' => $qt]);
}
}
return redirect()->back();
}
the probelem is in my blade i remove the comment from the input value it return this error Attempt to read property "quatity" on null i don't know what to do this is the third day already
<div class="quantity">
<a href="{{route('decrQtePanier',['id'=> $prod->id])}}" class="quantity-button minus">
<i class="klbth-icon-minus"></i>
</a>
<input value="{{--$prod->pivot->quatity--}}" name="cart[15945][qty]" type="text" id="quantity_61a9f089c4906" class="input-text qty text" step="1" min="1" max="11" size="4" placeholder="" inputmode="numeric" />
<a href="{{route('incrQtePanier',['id'=> $prod->id])}}" class="quantity-button plus">
<i class="klbth-icon-plus"></i>
</a>
</div>
<a style="text-decoration:none; " href="{{ url('add-to-cart/'.$prod->id) }}">
<button style="border-radius: 50px; padding:0 20px; margin-left:40px" type="submit" name="add-to-cart" value="352" class="single_add_to_cart_button button alt">
Ajouter
</button>
</a>
this is my cart module
use HasFactory;
protected $fillable = ['user_id'];
public function user()
{
return $this->belongsTo('App\Models\User');
}
public function produits()
{
return $this->belongsToMany('App\Models\Produit','produits_paniers')
->withPivot('quantite');
}
and this is my product module
use HasFactory;
protected $fillable = [
'nom', 'prix', 'prixpromo', 'detals', 'image','categorie_id','user_id'
];
public function favories()
{
return $this->belongsToMany('App\Models\Favorie');
}
public function paniers()
{
return $this->belongsToMany('App\Models\Panier');
}
public function commandes()
{
return $this->belongsToMany('App\Models\Commande');
}
public function categories()
{
return $this->belongsTo('App\Models\Categorie','categorie_id');
}
this is my routes this operation i'm using is in the detail route i'm newbe and i'm really stuck in here
Route::get('/detail/{id}', 'App\Http\Controllers\HomePageController#product_detail');
Route::get('/decreasePanier/{id}', 'App\Http\Controllers\PanierController#decrease')->middleware('auth')->name("decrQtePanier");
Route::get('/increasePanier/{id}', 'App\Http\Controllers\PanierController#increase')->middleware('auth')->name("incrQtePanier");