Hello,
Please run one of the included examples standalone and using PHP CLI mode to test if the library is working on your server.
As you're using a framework, maybe you didn't include the autoloader of phpdocx to be able to use the library? Please check your server logs.
About this line:
$docx->createDocx('../word_documents/hello_world');
It seems very strange, because a relative path like this one in a framework is not the public folder, so maybe it's wrong or the web server can't write in the folder.
Regards.