Dynamic Sort CPT

archive-ac_films.php

<?php

function ac_sort_buttons() {
    echo '<p>';
        echo 'Sort:';
        echo '<a href="?sort=oldest">Oldest</a>';
        echo '<a href="?sort=alpha">Alphabetical</a>';
        echo '<a href="?sort=random">Random</a>';
        echo '<a href="?sort=all">Show All</a>';
    echo '</p>';
}

functions.php

<?php
 
/**
 * Dynamic Sorting
 * 
 */
 
function ac_dynamic_sort_films( $query ) {
	if ( $query->is_main_query() && !is_admin() && $query->is_post_type_archive( 'ac_films' ) ) {
		if ( isset($_GET['sort']) == 'oldest' ) {
			$query->set( 'order', 'DESC' );
		}
		if ( isset($_GET['sort']) == 'alpha' ) {
			$query->set( 'orderby', 'title' );
		}
		if ( isset($_GET['sort']) == 'random' ) {
			$query->set( 'orderby', 'rand' );
		}
		if ( isset($_GET['sort']) == 'all' ) {
			$query->set( 'posts_per_page', '-1' );
		}
	}
}
add_action( 'pre_get_posts', 'ac_dynamic_sort_films' );