WordPress post tag & custom field

3 comments

1. To convert the old custom fields, you can write a plugin that, on activation, fetches all the posts with your custom field name and converts them to tags with the handy wp_set_post_terms.

   First set up a few constants with your field names and post type.

   <?php
   /**
    * CHANGE THIS! what is your custom field's name?
    */
   define( 'WPSE29498_FIELD', 'custom_field_name' );
   
   
   /**
    * CHANGE THIS! what post type?
    */
   define( 'WPSE29498_TYPE', 'post' );
   

   Then the activation hook function:

   <?php
   register_activation_hook( __FILE__, 'wpse29498_field_to_tag' );
   function wpse29498_field_to_tag()
   {
       $posts = get_posts(
           array(
               'post_type'     => WPSE29498_TYPE,
               'post_status'   => array( 'publish', 'draft', 'pending', 'future' ),
               'numberposts'   => -1,
               'meta_key'      => WPSE29498_FIELD
           )
       );
   
       if( empty( $posts ) ) return;
   
       foreach( $posts as $p )
       {
           if( $meta = get_post_meta( $p->ID, WPSE29498_FIELD, true ) )
           {
               wp_set_post_terms( $p->ID, $meta, 'post_tag', true );
           }
       }
   }
   

   And finally, you can hook into save_post and see if the custom field value is there. If so, make sure it’s not a term already, then insert it if it isn’t.

   Not sure if this is something you needed or a one time conversion.

   <?php
   add_action( 'save_post', 'wpse29498_save_post' );
   function wpse29498_save_post( $post_id )
   {
       if( $meta = get_post_meta( $post_id, WPSE29498_FIELD, true ) )
       {
           // get the current post tag
           $terms = wp_get_object_terms( $p->ID, 'post_tag', 'name' );
   
           // if our term is already there, bail
           if( in_array( $meta, $terms ) ) return;
   
           // add the term if not
           wp_set_post_terms( $post_id, $meta, 'post_tag', true );
       }
   }
   

   As a plugin.

   Log in to Reply

2. As far as I am aware, this isn’t possible to do automatically “out of the box”. A quick Google and it looks like there are currently no plugins that will do the job for you.

   However, I can’t see any reason why a plugin couldn’t be written to do this. You’ll need to use the “save_post” hook, which will run every time a post is saved/updated, check the custom field and apply it as a tag.

   Documentation on this particular hook is sparse, but it’s mentioned here:

   http://codex.wordpress.org/Plugin_API/Action_Reference

   Log in to Reply

3. I ran into a similar question a while ago from someone asking how to automatically add keywords from the All-in-one SEO plugin as post tags (http://www.vidalquevedo.com/how-to-add-tags/#li-comment-62)

   After I saw your question, I took that script I wrote and modified it to automatically add custom field values as post tags as well.

   Here’s the link to the script and post: http://www.vidalquevedo.com/wordpress-how-to-automatically-convert-custom-fields-to-post-tags/

   Thanks, and please let me know if that helps!

   Vq.

   Log in to Reply