Hello,
You can get that information using the following method:
https://www.phpdocx.com/api-documentation/docxutilities/indexer-parse-word-documents-with-PHP
If you need to query by a specific placeholder tag, you can use this method:
https://www.phpdocx.com/api-documentation/docx-path/get-docx-path-query-info
using a custom query.
Regards.