Hello,
The current version of phpdocx don't include a method to get that information from Word. We have added a task to include support in the next release of phpdocx for the Indexer class.
Although it can't be done using a method from phpdocx using the current version of the library, it could be done parsing the XML manually:
The size of an image is set by two tags:
<wp:extent cx="914400" cy="914400"/> image size
<wp:effectExtent b="0" l="0" r="0" t="0"/> effects of the image
The cx and cy values are EMUs:
EMUs are used for coordinates in vector-based drawings and embedded pictures. The EMU is a virtual unit to bridge both centimeters and inches. One inch equates to 914400 EMUs and a centimeter is 360000.
(https://startbigthinksmall.wordpress.com/2010/01/04/points-inches-and-emus-measuring-units-in-office-open-xml/)
Regards.