Flips the access rules for a post or posts so that users *without* any of the specified tags are granted access

wpf-flip-access-rules.php

<?php

add_filter('wpf_user_can_access', 'my_wpf_flip_access_rules', 10, 3);

function my_wpf_flip_access_rules( $can_access, $user_id, $post_id ) {

	// Optional: limit the rule flipping just to certain post IDs (1234 and 4567)
	if( $post_id != 1234 ) {
		return $can_access;
	}

	$post_restrictions = get_post_meta( $post_id, 'wpf-settings', true );

	if(empty($post_restrictions) || empty($post_restrictions['allow_tags'])) {
		return $can_access;
	}

	$user_tags = wp_fusion()->user->get_tags( $user_id );

	$result = array_intersect($user_tags, $post_restrictions['allow_tags']);

	if( empty($result) ) {

		// If user does *not* have any of the tags specified in the post restrictions, grant access
		return true;

	} else {

		// If user *does* have any of the tags, deny access
		return false;

	}

}