PHPExcel - undefined index: $ Cell.php line 809

PHPExcel cannot load spreadsheet with formula

PHP Notice:  Undefined index: $ in
/var/www/html/code.huypv.net/vendor/phpoffice/phpexcel/Classes/PHPExcel/Cell.php
on line 809 PHP Stack trace: PHP

As a "Quick and Dirty" hack, you might check the file Classes/PHPExcel/Cell.php and in the function rangeBoundaries, look for

// Uppercase coordinate
$pRange = strtoupper($pRange);
and try changing it to:

// Uppercase coordinate
$pRange = strtoupper(str_replace('$', '', $pRange));