menu item to display the most recent post

Question

I spent most of the day reviewing past questions and answers and have not found anything that addresses what I am trying to do. Maybe I didn't word my search correctly.

Lets say I have a category of posts for documents that reflect current committee members. I can create a WP menu item for a specific post with Wordpress However, users can submit new posts using the USP Pro plugin. Now the menu item needs to point to the most recently updated post. I want to avoid having to update the menu every time a new post is added.

I created a short code function in my functions.php file to get the most recent post for a category (short code argument). When I attempt to redirect to the permalink for that post, I get a blank page.

    //[latestpost]

function get_latest_post( $atts) {
    extract( shortcode_atts( array(
        'cat' => '',
    ), $atts, 'latestpost' ) );
    $args = array(
      'posts_per_page' => 1, // we need only the latest post, so get that post $
      'cat' => $cat, // Use the category id, can also replace with category_nam$
      //'category_name' => 'SLUG OF FOO CATEGORY,
     );
    $q = new WP_Query( $args);
    if ( $q->have_posts() ) {
        while ( $q->have_posts() ) {
            $q->the_post();
            //Your template tags and markup like:
            //the_title();
            $link=get_permalink($post);
 //       echo $link;
//        echo $cat;
            if ( wp_redirect( $link) ) {
                exit;
            }
        }
        wp_reset_postdata();
    }
}
add_shortcode('latestpost','get_latest_post')`


 

I put in a couple of echo statements to confirm that the function was getting the correct category ($cat) and permalink. They appear on the page but the page is not redirected.

Running Wordpress 5.1 with a twenty seventeen child theme.

Thanks for your help.

Answer 1

If you want to perform any redirects, you have to send your header before site sends any output.

Shortcodes are run when the content is obtained, parsed and printed. So the site will already be partially sent to the browser, so you won't be able to perform any redirects any more.

So you should run your code using some hook that is fired before any output is sent to the browser. You can use wp hook for example.

And if you really want the shortcode to cause redirection, then:

1. Display a link instead - it will be less confusing for users, I guess.
2. You'll have to do the redirection in JS:

.

function get_latest_post( $atts) {
    extract( shortcode_atts( array(
        'cat' => '',
    ), $atts, 'latestpost' ) );

    $args = array(
        'posts_per_page' => 1, // we need only the latest post, so get that post $
        'cat' => $cat, // Use the category id, can also replace with category_nam$
        //'category_name' => 'SLUG OF FOO CATEGORY,
    );
    $q = new WP_Query( $args);
    if ( $q->have_posts() ) {
        while ( $q->have_posts() ) {
            $q->the_post();

            // Your template tags and markup like:
            // the_title();
            $link=get_permalink($post);
            // echo $link;
            // echo $cat;
            echo '<script type="text/javascript>document.location.href = "' . $link . '";</script>'
            return;  // you want only one redirection in your site
        }
        wp_reset_postdata();
    }
}
add_shortcode( 'latestpost', 'get_latest_post' );