Describe the bug and add attachments

Description
During runtime, the application logs deprecation warnings originating from the PhpOffice/PhpWord library. The issue occurs in vendor/phpoffice/phpword/src/PhpWord/Reader/Word2007/AbstractPart.php at line 300, where htmlspecialchars() is invoked with a null value passed to its first parameter.

In PHP 8.1+, passing null to a parameter that requires string is deprecated. This leads to deprecation messages in the logs:

DEPRECATE: vendor/phpoffice/phpword/src/PhpWord/Reader/Word2007/AbstractPart.php line 300 user unknown -- htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated

Impact:

• No immediate runtime failure, but logs are polluted with warnings.
• Potential risk of stricter type enforcement in future PHP versions (e.g., PHP 9.0), which could escalate from a deprecation to a fatal error.
• Makes debugging and monitoring more difficult due to excessive warning noise.

Root Cause:
htmlspecialchars() is being called without verifying that the provided value is a string. When null is passed instead of an empty string, PHP raises a deprecation notice.

Environment:

• Library: phpoffice/phpword
• File: vendor/phpoffice/phpword/src/PhpWord/Reader/Word2007/AbstractPart.php
• PHP Version: 8.1+
• Affected Function: htmlspecialchars()

Expected behavior

1. PhpWord should never pass null to htmlspecialchars().
2. When a value is missing, it should gracefully fallback to an empty string ("") instead of producing deprecation warnings.
3. Application logs should remain clean, free of unnecessary deprecation messages.

Proposed Solution:

• Ensure that a string value is always passed to htmlspecialchars(). If the input is null, default to an empty string:

$value = $value ?? '';
htmlspecialchars($value, ENT_QUOTES, 'UTF-8');

Steps to reproduce

1. Use PhpWord to read or parse a Word 2007 (.docx) file. (Look at attached)
2. Trigger parsing of elements that result in null values being passed to htmlspecialchars() (empty table cell or paragraph).
3. Check application logs – a deprecation warning will appear.

table.docx

PHPWord version(s) where the bug happened

1.4.0

PHP version(s) where the bug happened

8.3

Priority

• I want to crowdfund the bug fix (with @algora-io) and fund a community developer.
• I want to pay the bug fix and fund a maintainer for that. (Contact @Progi1984)