Call to a member function extension() on array

I have tried to upload the image using Postman and the image is stored in the preferred directory and the name and is stored in database but i am getting the error response.

public function store(Request $request)
{
    $design_studio = new DesignStudio;
    $design_studio->user_id = 1;
    $design_studio->title = $request->title;
    $design_studio->lang = $request->lang;
    $design_studio->body = $request->body;
    if($request->has('image')) {
        $image = $request->file('image');
        $filename = $image->getClientOriginalName();
        $image->move(public_path('images/slideShow'), $filename);
        $design_studio->image = $request->file('image')->getClientOriginalName();
    }
    if ($sliders = $request->file('sliders')) {
        foreach ($sliders as $slider) {
            $filename = rand(111111, 999999);
            $extension = $request->file('sliders')->extension();
            $getFileExt = $filename + '.' +$extension;
            $slider->move(public_path('images/design-studios/'), $getFileExt);
            $data[] = $getFileExt;
        }
    }
    $design_studio->sliders = json_encode($data);
    $design_studio->save();
    $design_studio->categories()->attach($request->category);
    return redirect()->route('design-studios.index');
}