How can I tell if a post has been published at least once?

Question

I am working on a plugin that has a piece of meta data attached to each post. The fields are editable in a meta box on the post. This is all working fine.

I would like to prevent anyone from modifying the settings in meta box once the post has been published. By virtue of the application looking for this meta data, it doesn't make any sense for the meta data to change after publish.

So, is there any way to tell if a post has been published at least once? This way I can disable the controls in the meta box.

Answer 1

We can do this by storing the value into postmeta when post is published first time.

function save_ispublished( $post_id ) {

    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE)
        return;

    $published_once = get_post_meta( $post_id, 'is_published', true );

    // Check if 'is_published' meta value is empty.
    if ( ! empty( $published_once ) ) {

        $published_once = 'yes';
    }

    // store is_published value when first time published.
    update_post_meta( $post_id, 'is_published', $published_once );
}
add_action( 'save_post', 'save_ispublished' );

you can check it by get the meta value.

$is_published = get_post_meta( $post_id, 'is_published', true );

if( $is_published == 'yes' ) {

    /*
    * Actions if post is already published atleast once.
    */
}

Hope this help !

Answer 2

I totally agree with @Govind Kumar except for the action uses in the example, you can use publish_post action instead of save_post.

publish_post is an action triggered whenever a post is published, or if it is edited and the status is changed to publish. Save_post will trigger each time the post is save.

publish_post action