Wordpress previous_post_link() and next_post_link() don't work at CPT

Question

everyone!

There is a problem at Wordpress with CPT and ACF.

I have ACF fields ('previouspost' and 'nextpost) at my CPT "portfolio" posts. I need every post to get previous and next post links to ACF fields. Code, which I use don't make anything, fields are empty, no errors and warnings

function update_portolio_metadata(){

    $args = array(
        'post_type' => 'portfolio', // Only get the posts
        'post_status' => 'publish', // Only the posts that are published
        'posts_per_page'   => -1 // Get every post
    );
    $posts = get_posts($args);
    foreach ( $posts as $post ) {
            $previouslink = previous_post_link();
            $nextlink = next_post_link();


    update_post_meta( $post->ID, 'previouspost', $previouslink);
    update_post_meta( $post->ID, 'nextpost', $nextlink);


    }
}
add_action('init','update_portolio_metadata');

Updated, checked and work

function update_portolio_metadata(){
    $args = array(
            'post_type' => 'portfolio', // Only get the posts
            'post_status' => 'publish', // Only the posts that are published
            'posts_per_page'   => -1 // Get every post
    );
    $loop = new WP_Query( $args );
    while ( $loop->have_posts() ) : $loop->the_post();
        $previouslink = get_permalink(get_adjacent_post(false,'',false));
        $nextlink = get_permalink(get_adjacent_post(false,'',true));
            
        update_post_meta( get_the_ID(), 'previouspost', $previouslink);
        update_post_meta( get_the_ID(), 'nextpost', $nextlink);
    endwhile;
}


add_action('init','update_portolio_metadata');

Answer 1

There functions works in the loop only. You can use wp_query instead of get_posts.

Your code should be like this:

$loop = new WP_Query( $args );
while ( $loop->have_posts() ) : $loop->the_post();
    $previouslink = get_previous_post_link();
    $nextlink = get_next_post_link();

    update_post_meta( get_the_ID(), 'previouspost', $previouslink);
    update_post_meta( get_the_ID(), 'nextpost', $nextlink);
endwhile;
}