wp_set_object_terms( int $object_id, string|int|array $terms, string $taxonomy, bool $append = false ): array|WP_Error

User Contributed Notes

1. Skip to note 6 content

   Darko G. 5 years ago

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   Be careful when adding existing terms to object!

   The second parameter $terms (eg. category id) needs to be of type integer or array of integers.

   Note: If you provide a string value for $terms, WordPress will create new term named after the $terms value and not pick existing term by term_id. This happens because the $terms must be integer or array of integers.

   Wrong:

   $post_id = 15;
   $category_id = '14';
   $taxonomy = 'category';
   wp_set_object_terms( $post_id, $category_id, $taxonomy );

   Correct:

   With the intval() function we cast the second parameter to integer. You can also use (int) $category_id

   $post_id = 15;
   $category_id = 14;
   $taxonomy = 'category';
   wp_set_object_terms( $post_id, intval( $category_id ), $taxonomy );

   • Please note that the “Term taxonomy IDs of the affected terms” are returned as strings, which is rather ironic considering that you must supply an array of term integers as the second argument (if using IDs instead of terms).

     pmnip 7 months ago
2. Skip to note 7 content

   Codex 9 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 3You must log in to vote on the helpfulness of this note

   Setting a Post’s Categories

   If you want to set the categories of a post with the ID of 42:

   <?php
   
   // An array of IDs of categories we want this post to have.
   $cat_ids = array( 6, 8 );
   
   /*
    * If this was coming from the database or another source, we would need to make sure
    * these were integers:
   
   $cat_ids = array_map( 'intval', $cat_ids );
   $cat_ids = array_unique( $cat_ids );
   
    */
   
   $term_taxonomy_ids = wp_set_object_terms( 42, $cat_ids, 'category' );
   
   if ( is_wp_error( $term_taxonomy_ids ) ) {
   	// There was an error somewhere and the terms couldn't be set.
   } else {
   	// Success! The post's categories were set.
   }

   Note that this will set a post’s categories to be exactly the array you pass, any categories the post previously had will be removed from the post. See the next example.
3. Skip to note 8 content

   Codex 9 years ago

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   Removing All Categories From a Post

   If you want to clear/remove all categories from a post, you can pass an empty value for $terms:

   <?php wp_set_object_terms( 42, null, 'category' ); ?>
4. Skip to note 9 content

   zenith 3 years ago

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   I hope this helps someone when using this function with wp_insert_post() and/or wp_update_post().

   $post_args = [
'post_title' => $title,
'post_status' => 'publish',
'post_type' => $pt,
'post_content' => $content,
];

   $new_post_id = wp_insert_post($post_args);

   wp_set_object_terms($new_post_id->ID === null ? $new_post_id : $new_post_id->ID, array(intval($term_id)), $tax);


   On post creation – $new_post_id exists as an int(id), however, when updating the post, $new_post_id exists as the post object

   To counteract this $new_post_id->ID will fetch the int after post is created, but not before, therefore, using $new_post_id->ID will not work as it doesn’t exist yet

   So set $new_post_id first only if $new_post_id->ID returns null, otherwise use the ID from the object

   This confused me and many many others for ages, so hopefully, this will help someone.
5. Skip to note 10 content

   Codex 9 years ago

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   Adding Categories to a Post

   If you want to add categories to a post while keeping the categories it has already, you need to pass true for the $append parameter:

   <?php
   
   // An array of IDs of categories we to add to this post.
   $cat_ids = array( 6, 8 );
   
   /*
    * If this was coming from the database or another source, we would need to make sure
    * these were integers:
   
   $cat_ids = array_map( 'intval', $cat_ids );
   $cat_ids = array_unique( $cat_ids );
   
    */
   
   // Add these categories, note the last argument is true.
   $term_taxonomy_ids = wp_set_object_terms( 42, $cat_ids, 'category', true );
   
   if ( is_wp_error( $term_taxonomy_ids ) ) {
   	// There was an error somewhere and the terms couldn't be set.
   } else {
   	// Success! These categories were added to the post.
   }