This type of call, http://example.com/wp-content/plugins-themes/whatever/file.php
, is not correct. No plugin or theme file is made to work like this (it can be, but on rare and specially coded occasions).
This way works:
jQuery('<div ></div>').load('http://example.com/some-real-page-url/').modal();
Create a page with the desired template (some-real-page-url
) and load it in your AJAX call.
But I tested the simple modal with TwentyEleven/Twelve/Thirteen and it did not behave well. Maybe the Page Template will have to be heavily customized, i.e., your own header instead of get_header()
.