Both plugins I have tried use shortcodes.
One you enter the code on the page between [insert_php] & [/insert_php] dropping the <?php & ?> Code goes where the & is.
The other plugin you add your php (again without the <?php & ?>) in the plugins optins page (the same way you do with custom css). Then you add the shortcode that references the code eg [xyz-ips snippet=”Pagination”]
Both plugins give the same result. You get all the text and the pagination buttons in the first section, then subsequent sections are posts and finally there is a blank section at the end. It is completely irrelevant which order you have the shortcodes and text on the page, it always publishes like this.