If you are using addhtml() for generating a .docx file, you must remember that PHPdocX is very smart, but Word don’t understand things like “medium” or “big”.

Code like this:

<p>This will insert the name in the document: <strong><span style="font-size: medium;">The Name</span></strong></p>

Will be no rendered. You must specify the font size as pixels on font-size’s tag like this:

<p>This will insert the name in the document: <strong><span style=" font-size: 12px;”>The Name</span></strong></p>