Duplicate Content Issue with WordPress Permalink Structure and Primary Categories

Question

I have this permalink structure in wordpress /%category%/%postname%/

now suppose i have written a article article with title "Hello World" and i selected two categories for this article "cat1" and "cat2" now "cat1" is my primary category and i selected this using RankMath Plugin

just because "cat1" is my primary category for that post the url become

https://example.com/cat1/hello-world/ when we go to this the post "Hello World" is loaded.

but when I manually go to the same post with "cat2" https://example.com/cat2/hello-world/ the same article "Hello World" is loaded.

Now https://example.com/cat1/hello-world/ & https://example.com/cat2/hello-world/ both urls are working individually and this is a problem

this url with secondary category https://example.com/cat2/hello-world/ should get 404 or automaticllay redirect to primary category url https://example.com/cat1/hello-world/

but the problem is if same post is working with "cat2" also

this way i have two url for same article, how to fix this? Please Help.

Answer 1

function get_current_post_ID() {
    $postid = get_queried_object_id();
    $post_url = get_permalink( $postid );
    //wp_redirect( $post_url );
    if( has_category('', $postid) && urldecode('https://'.$_SERVER ['HTTP_HOST'].$_SERVER ['REQUEST_URI']) != $post_url ) :
        wp_redirect( $post_url, 308 );
        exit();
    endif;
}
add_action( 'template_redirect', 'get_current_post_ID' );