How can I set a meta value that will then affect other post meta values?

Question

I have a metabox on my post type of 'ebrd_videos' that sets the video as a 'featured video' using a checkbox.

I would like to limit the number of videos with the status of 'featured = on' to 1. So that when I set a video as featured, and publish/update that video, all other videos are set to 'featured = off'.

If it helps, here is the code to create the meta box:

// Add the Top and Featured News Meta Boxes ----------------------------------------//

add_action( 'add_meta_boxes', 'ebrd_add_post_metaboxes' );

function ebrd_add_post_metaboxes() {
    add_meta_box('ebrd_feat', 'Post status', 'ebrd_feat', 'ebrd_videos', 'side', 'default');
}

// Featured Metabox

function ebrd_feat(){
    global $post;
    $custom = get_post_custom($post->ID);
    if(isset($custom["ebrd_home_feat"][0])) $ebrd_home_feat = $custom["ebrd_home_feat"][0];
    else $ebrd_home_feat = 'off';

    // We'll use this nonce field later on when saving.  
    wp_nonce_field( 'my_meta_box_nonce', 'meta_box_nonce' ); 
?>

<input type="checkbox" name="ebrd_home_feat" <?php if( $ebrd_home_feat != 'off' ) { ?>checked="checked"<?php } ?> />  Home feature?
<?php
} 

add_action('save_post', 'save_details');

function save_details($post_ID = 0) {
    $post_ID = (int) $post_ID;
    $post_type = get_post_type( $post_ID );
    $post_status = get_post_status( $post_ID );

    // if our nonce isn't there, or we can't verify it, bail 
    if( !isset( $_POST['meta_box_nonce'] ) || !wp_verify_nonce( $_POST['meta_box_nonce'], 'my_meta_box_nonce' ) ) return;

    // if our current user can't edit this post, bail  
    if( !current_user_can( 'edit_post' ) ) return; 

    if(isset($_POST["ebrd_home_feat"])) $ebrd_home_feat = $_POST["ebrd_home_feat"];
    else $ebrd_home_feat = 'off';

    if ($post_type) {
        update_post_meta($post_ID, "ebrd_home_feat", $ebrd_home_feat);
    }
   return $post_ID;
}

Answer 1

If you really want to have only one post id and a value attached to it, well i think it will be better to store in options table using add_option and then using it using get_option..... that way you will be saved from headache of updating all posts meta at once when any of post is updated.....