If value exist in database don't save Laravel - php

Question

I'm creating a wishlist where the user can save his own products and save them. What I want is that a user can't save a product more than one time.
So, what I'm doing is, if the product_id exists in the DB, I don't want to save the new record.
This is my code, what am I doing wrong?
public function addWishlist(Wishlist $wishlist) {
$wishlist->user_id = request('user_id');
$wishlist->product_id = request('product_id');
if(DB::table('wishlists')->where('product_id' !== $wishlist->product_id)) {
$wishlist->save();
return redirect()->back();
}
}

Answer 1

what about this
public function addWishlist(Wishlist $wishlist) {
$userId = request('user_id');
$productId = request('product_id');
$found = Wishlist::where('user_id', $userId)->where('product_id', $productId)->count();
if($found == 0) {
$wishlist->user_id = $userId;
$wishlist->product_id = $productId;
$wishlist->save();
return redirect()->back();
}
}

Answer 2

public function addWishlist(Wishlist $wishlist) {
if(DB::table('wishlists')->where(['user_id'=>$user_id,'product_id'=>$wishlist->product_id])->exists()){
// record already exist
return redirect()->back();
}else{
// record not exist , save the record
$withlist = new Wishlist();
$wishlist->user_id = request('user_id');
$wishlist->product_id = request('product_id');
$wishlist->save();
return redirect()->back();
}
}

Answer 3

You can use firstOrNew and you need to check with user_id and product_id combination
$wishlist::firstOrNew(array('user_id' => request('user_id'),'product_id'=>request('product_id')));
$wishlist->user_id = request('user_id');
$wishlist->product_id = request('product_id');
$wishlist->save();
return redirect()->back();

Answer 4

Have you tried firstOrCreate()
$user = User::firstOrCreate(['email' => $email])