Problem with isFormula() / Calculation::CALCULATION_REGEXP_CELLREF

[billynoah]

This is:

- [x] a bug report
- [ ] a feature request
- [x] **not** a usage question (ask them on https://stackoverflow.com/questions/tagged/phpspreadsheet or https://gitter.im/PHPOffice/PhpSpreadsheet)

What is the expected behavior?

In PhpSpreadsheet/Calculation/Functions.php the function isFormula() uses regex Calculation::CALCULATION_REGEXP_CELLREF which should be able to successfully parse $cellReference.

What is the current behavior?

Regex Calculation::CALCULATION_REGEXP_CELLREF fails to parse $cellReference. Actually - the regex is not even checked before referencing $matches.

What are the steps to reproduce?

In the spreadsheet I am trying to read when I echo $cellReference I get: Load Sheet!F3. The regex fails in this case and so the following lines reference keys which do not exist since $matches is empty:

$cellReference = $matches[6] . $matches[7];
$worksheetName = str_replace("''", "'", trim($matches[2], "'"));

At the very least there should be a check like:

if preg_match(...) {

And probably, the regex Calculation::CALCULATION_REGEXP_CELLREF should be updated to address this case.

Please provide a Minimal, Complete, and Verifiable example of code that exhibits the issue without relying on an external Excel file or a web server:

<?php

require __DIR__ . '/vendor/autoload.php';
PhpOffice\PhpSpreadsheet\IOFactory::load('test_case.xlsx');

Using this file for testing: test_case.xlsx

Which versions of PhpSpreadsheet and PHP are affected?

This has been an ongoing issue and affects 1.18.0 (Current version) + all previous versions I have used

[PowerKiKi]

Fixed in 1.19.0