I also encountered a similar problem, and I haven't been able to solve it yet.

my way to solve it:
override PHPWord/src/PhpWord/TemplateProcessor.php in composer.json
and replace
return $subject ? Text::toUTF8($subject) : ''; >>> return (null !== $subject) ? Text::toUTF8($subject) : '';

Thanks @truestealth - works great!

As a workaround, you could prepend the 0 with a zero width no-break space:

$templateProcessor->setValue('test', mb_chr(hexdec('FEFF')) . '0');

I encountered a similar issue when trying to pass a string "0" to the template processor, and eventually fixed it by adding a zero width space character to the string, so it doesn't get evaluated as false-y thus reducing it to an empty string:

'0' . "\u{200B}"

+1, we are running into this issue as well. Hope the fix gets merged soon. Thank you all for your workarounds.

As a workaround, you could prepend the 0 with a zero width no-break space:

$templateProcessor->setValue('test', mb_chr(hexdec('FEFF')) . '0');

Thanks, works like a charm!

Bump for a fix

I encountered a similar issue when trying to pass a string "0" to the template processor, and eventually fixed it by adding a zero width space character to the string, so it doesn't get evaluated as false-y thus reducing it to an empty string:

'0' . "\u{200B}"

Thanks, it works, while "\u{200B}" displays as a space, "\u{200D}" looks better cause it is invisible.