How to add terms to a post depending on its title?

1 comment

1. You have to check the existing terms first with wp_get_object_terms() and if the term you need is missing, add it with wp_set_object_terms().

   It is faster to update the terms just once than to do this for every term.

   The following example is running on save_post. I put everything into a class (and into a plugin) to make the code more readable. You could use just one function tough.

   To keep things flexible I implemented three matching algorithms: exact, case-insensitive and regular expression (regex).
   The terms must exist already. I choose this requirement to prevent accidental mismatches.

   <?php # -*- coding: utf-8 -*-
   /**
    * Plugin Name: T5 Term by title
    */
   add_action( 'save_post', array ( 'WPSE_39700_Term_By_Title', 'init' ), 10, 2 );
   
   class WPSE_39700_Term_By_Title
   {
       /**
        * Post types to process.
        *
        * @var array
        */
       protected $post_types = array ( 'post', 'page' );
   
       /**
        * What to search for? Adjust this to your needs.
        *
        * @var array
        */
       protected $searches = array (
           'Dog Training' => array (           // string to search for
               'search_type' => 'exact',       // 'exact', 'case-insensitive' or 'regex'
               'taxonomy'    => 'category',    // existing taxonomy
               'term'        => 'Dog Training' // existing term name
           ),
           '~ds*(kg|kilogram)~i' => array ( // '43kg' or '3 kilogram'
               'search_type' => 'regex',
               'taxonomy'    => 'post_tag',
               'term'        => 'Health'
           ),
           'wordpress' => array (
               'search_type' => 'case-insensitive',
               'taxonomy'    => 'post_tag',
               'term'        => 'WordPress'
           )
       );
   
       /**
        * Current post object.
        *
        * @var object
        */
       protected $post = NULL;
   
       /**
        * Terms to update.
        *
        * @var array
        */
       protected $update = array ();
   
       /**
        * Initial callback function.
        *
        * @wp-hook save_post
        * @param   int    $post_id
        * @param   object $post
        * @return  void
        */
       public function init( $post_id, $post )
       {
           new self( $post_id, $post );
       }
   
       /**
        * Constructor called by init.
        *
        * @param int    $post_id
        * @param object $post
        */
       public function __construct( $post_id, $post )
       {
           // wrong post type
           if ( ! in_array( $post->post_type, $this->post_types )
               // no title
               or '' === trim( $post->post_title )
           )
           {
               return; // Nothing to do.
           }
   
           $this->post = $post;
   
           foreach ( $this->searches as $search => $properties )
           {
               if ( $this->has_match( $search, $properties['search_type'] ) )
               {
                   $this->add_term( $properties['term'], $properties['taxonomy'] );
               }
           }
           $this->write_terms();
       }
   
       /**
        * Does the title contain our search phrase?
        *
        * @param  string $search
        * @param  array  $type
        * @return bool
        */
       protected function has_match( $search, $type )
       {
           switch ( $type )
           {
               case 'case-insensitive':
                   // It may return 0, but that's not the same as FALSE.
                   return FALSE !== stripos( $this->post->post_title, $search );
               case 'regex':
                   return preg_match( $search, $this->post->post_title, $m );
               default:
                   return FALSE !== strpos( $this->post->post_title, $search );
           }
       }
   
       /**
        * Adds the term to the post.
        *
        * @param  string $term
        * @param  string $taxonomy
        * @return void
        */
       protected function add_term( $term, $taxonomy )
       {
           if ( empty ( $this->update[ $taxonomy ] ) )
           {
               $this->update[ $taxonomy ] = wp_get_object_terms(
                   $this->post->ID,
                   $taxonomy,
                   array ( 'fields' => 'name' )
               );
           }
   
           if ( get_term_by( 'name', $term, $taxonomy ) )
           {
               $this->update[ $taxonomy ][] = $term;
               $this->update[ $taxonomy ] = array_unique( $this->update[ $taxonomy ] );
           }
       }
   
       /**
        * Takes all terms from $update and relates them to the current post.
        *
        *  @return void
        */
       protected function write_terms()
       {
           if ( ! empty ( $this->update ) )
           {
               foreach ( $this->update as $taxonomy => $terms )
               {
                   wp_set_object_terms( $this->post->ID, $terms, $taxonomy );
               }
           }
       }
   }
   

   Here I have written a post with the title a test with wORdpReSs and 22kg Dog Training and then I hit Save Draft once:

   

   To update existing posts run something like the following once:

   $posts = get_posts( array ( 'numberposts' => - 1 ) );
   foreach ( $posts as $post )
   {
       new WPSE_39700_Term_By_Title( $post->ID, $post );
   }
   

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