Hello,
You can use getActiveSlideInformation (https://www.phppptx.com/documentation/api-documentation/layouts-settings/get-active-slide-information-pptx) to get the existing layout placeholders from a slide. This method is available in all licenses. On the practical guide is fully detailed the use of this method:
Indexer can also extract information from a PPTX such as layouts. But this method is only available in Advanced and Premium licenses.
Please note that trial package includes the Basic license features (adding trial watermarks).
Advanced and Premium licenses include many extra features: https://www.phppptx.com/features
For example a stream mode to generate PPTX files without creating a file in the fs (https://www.phppptx.com/documentation/api-documentation/performance/zip-stream-pptx).
Regards.