Updated version of php from 7.3 to 7.4.

I updated version of php from 7.3 to 7.4. In this i'm getting, error message in first line of code like Array and string offset access syntax with curly braces is deprecated. Here is my code

$excel=(string) Excel::create('Fees_' . date('dmy'), function($excel) use ($fees_array,$count){

$excel->setTitle('Fees_' . date('dmy'));

$excel->sheet('Fees_' . date('dmy'), function($sheet) use ($fees_array,$count){

$sheet->fromArray($fees_array, null, 'A1', false, false);

$sheet->cell('A1:Z1', function ($cells) {

$cells->setFontWeight('bold');

});

$sheet->setWidth('A', 5);

$sheet->cell('A1:A'.$count, function($cells) {

$cells->setAlignment('center');

});