The abort_unless function throws an HTTP exception if a given boolean expression evaluates to false:
<?php abort_unless(Auth::user()->isAdmin(), 403);
<?php     public function handle($filename)

    {

        abort_unless(request()->hasValidSignature(), 401);



        return Utils::pretendPreviewResponseIsPreviewFile($filename);

    }
<?php     public function handle()

    {

        abort_unless(request()->hasValidSignature(), 401);



        $disk = FileUploadConfiguration::disk();