Laravel 5.1 Max image size

I'm using Laravel 5.1 and php 7. I try to implement an image upload. Large images fails to upload. (A white screen appears with no error message) I tested it locally on xampp and on a webspace. With small images it works. It fails with an image of 2.5MB but the max value is 5000.

My controller:

public function fileUpload(Request $request)

{

     $this->validate($request, [

        'image' => 'required|image|mimes:jpeg,png,jpg,gif,svg|max:5000',
     ]);


     $image = $request->file('image');

     $input['imagename'] = time().'.'.$image->getClientOriginalExtension();

     $destinationPath = public_path('/images');

     $image->move($destinationPath, $input['imagename']);


    $this->postImage->add($input);


    return back()->with('success','Image Upload successful');

}

The questions:

1. Why there is no error message? Only a white screen appears when it fails to upload. (Maybe there is a necessary configuration to do in one of the laravel config files?
2. Why it works with smaller images? Where in xampp and on the webspace it's a configuration necessary?

via Chebli Mohamed