Undefined variable – bootstrap pagination – Laravel

I have a controller that filter data from the database an send it to the view where i am using bootstrap pagination to show it on multiple pages… the data get listed on the view and every Everything work fine, but the problem is when i try to go the second page i get this error: Undefined variable: filtredPosts

this is the controller.

public function filter(Request $request){
    $query = Post::query();
    if ($request->country){
        $query->where('country','=',$request->country);
    }
    if($request->city){
        $query->where('city','=',$request->city);
    }
    if($request->type){
        $query->where('type','=',$request->type);
    }
    if($request->sortby){
        if ($request->sortby=='newest'){
            $filtredPosts = $query->orderBy('created_at', 'desc')->paginate(9);
            $sortby = 'newest';
        }elseif ($request->sortby=='oldest'){
            $filtredPosts = $query->orderBy('created_at', 'asc')->paginate(9);
            $sortby = 'oldest';
        }
    }

    return view('posts.postDashboard',['posts'=>$filtredPosts, 'sortby'=>$sortby, 'country'=>$request->country,'city'=>$request->city,'type'=>$request->type]);
}

Answers:

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Method 1

Your variable filtredPosts is defined only if the $request->sortby is present.
If your request doesn’t have a sortby key, this variable will be undefined.

You can solve it defining the variable before the if($request->sortby) check:

...
$filtredPosts = $query;

if($request->sortby){
    if ($request->sortby=='newest'){
        $filtredPosts = $query->orderBy('created_at', 'desc')->paginate(9);
        $sortby = 'newest';
    }elseif ($request->sortby=='oldest'){
        $filtredPosts = $query->orderBy('created_at', 'asc')->paginate(9);
        $sortby = 'oldest';
    }
}

Also, in your blade view, you need to pass the query string to the pagination using

$posts->withQueryString()->links();

Method 2

You did not provide your pagination code on your blade, may be its something like :

{{ $posts->links() }}

You need to pass extra parameter with appends on Paginator method, like :

{!! $posts->appends(['sortby' => $sortby, 'country' => $country, 'city' => $city])->links() !!}

On Laravel 7 or above version, you can call the withQueryString() method on your Paginator instance :

{!! $posts->withQueryString()->links() !!}

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0