Question

I have a php function that generates a comma separated list of Post IDs that specify the order those posts should display on my WordPress site.

I’m looking for a place I can insert an SQL query like:

SELECT * FROM wp_posts WHERE ID IN ('1', '2', '3')

Which .php file should I modify? How should I phrase the SQL?

Answer 1

First off you should use wp_query for this. It is designed to query posts.

<?php
$args = array(
    'post__in' => array ( 1,2,3) //the Ids
);
$query = new WP_Query($args);
if ($query->have_posts()){
    while ($query->have_posts()) {
        $query->the_post();
        echo get_the_ID().'<br/>';
    }

} else {
    echo 'no posts found';
}

About the placement
I advise to do it in a custom template, make a simple template with the code above, create a page assign it that template and make the page private.