Array and string offset access syntax with curly braces is deprecated in php-7.4.19-Win32-vc15-x64

I have this old project with importing excel data to db,i am using laragon with latest version with php-7.4.19-Win32-vc15-x64 but the project is run with 7.1 in the server so i have used php-7.1.25-Win32-VC14-x64 this php version,but when i try to upload excel it throws this error I have searched also found using [] instead of {} will fix the issue,but i have tried that, this is line where showed the error but i tried to use [] this but same error throws }); return back()->with('success', 'Your File Is Successfully Uploaded To Database!');

public function importExcel(Request $request)
{
    if ($request->hasFile('import_file')) {

        Excel::load($request->file('import_file')->getRealPath(), function ($reader) {
            foreach ($reader->toArray() as $key => $row) {
                
                $old_customer = Registration::where('customerid', $row['customerid'])->first();
                if(count($old_customer)==0)
                {

                $data['customername'] = $row['customername'];
                $data['chassis'] = $row['chassis'];
                $data['model'] = $row['model'];
                $data['branchcode'] = $row['branchcode'];
                $data['delivery'] = $row['delivery'];
                $data['customerid'] = $row['customerid'];
                $data['phone'] = $row['phone'];
                $data['invoicedate'] = $row['invoicedate'];
                
                $registration_id = Registration::orderBy('registration_id', 'desc')->take(1)->get();

                if (count($registration_id) > 0) {
                    $regid = $registration_id[0]->registration_id;
                    $regid = $regid + 1;

                } else {
                    $regid = 1;
                }

                $register = new Registration();
                $register->registration_id = $regid;
                $register->customername = $row['customername'];
                $register->chassis = $row['chassis'];
                $register->model = $row['model'];
                $register->branchcode = $row['branchcode'];
                $register->delivery = $row['delivery'];
                $register->customerid = $row['customerid'];
                $register->phone = $row['phone'];
                $register->invoicedate = $row['invoicedate'];
                $register->created_user_id = Session::get('created_id');
                $register->save();

                $regidn = Registration::orderBy('registration_id', 'desc')->get();
                $regidd = $regidn[0]->registration_id;
                $ssitrack = new Ssi_track();
                $ssitrack->registration_id = $regid;
                $ssitrack->ssi_track_id = $regid;
                $ssitrack->save();
                $ssitrackk = Ssi_track::orderBy('ssi_track_id', 'desc')->get();
                $ssitrackk = $ssitrackk[0]->registration_id;

                }
                
            }
        });
      return back()->with('success', 'Your File Is Successfully Uploaded To Database!');
    }
    return back()->with('success', 'File Doesnt Uploaded!');
}

via Chebli Mohamed