Pagination with different posts_per_page

Issue Description

Main blog pulls through say 6 posts. Then we have a custom post type where we use 3 posts. Pagination always breaks.

Code Snippets

function case_studies_pagination( $query ) {

	//Are we on case studies?
	if (get_query_var('post_type') == "cpt_casestudies") {

		$query->set( 'posts_per_page', 6 );

	}

}
add_action( 'pre_get_posts', 'case_studies_pagination' );

How to Fix the Issue

Use ‘pre_get_posts’, check we are on the right archive page, then set ‘posts_per_page’

Need to be careful here as we are setting the number of posts per page in a second place, so if we change this on the archive page, it needs changing here too.

References