修改PHPExcel兼容php7.4
https://blog.csdn.net/u012931845/article/details/133899174
D:\phpstudy_pro\WWW\yingxin\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Cell\DefaultValueBinder.php
修改第56行为
} elseif (is_array($pValue) && $pValue[0] === '=' && strlen($pValue) > 1) {
