WordPress provides a wide variety of functions to help developers manage taxonomies and tags on their websites. One of the most useful of these is the wp_set_object_terms function.
The wp_set_object_terms function is used to assign one or more terms (such as tags or categories) to a specified post, page, or custom post type. This function can be used to add new terms to a post or to replace existing ones. It is also possible to use this function to remove terms from a post.
The wp_set_object_terms function takes three parameters: the ID of the object (post, page, or custom post type) to which you want to add or remove terms, the term or terms you want to add or remove, and the name of the taxonomy (such as "category" or "post_tag") to which the terms belong.
Here is an example of how to use wp_set_object_terms to assign a new term to a post:
// Set the ID of the post you want to update
$post_id = 123;
// Set the name of the term you want to add
$term_name = 'New Term';
// Set the name of the taxonomy to which the term belongs
$taxonomy = 'category';
// Use wp_set_object_terms to add the new term to the post
wp_set_object_terms( $post_id, $term_name, $taxonomy );In this example, the wp_set_object_terms function is used to add a new term called "New Term" to the "category" taxonomy for a post with the ID of 123.