WordPress: Add term to post

add-term-to-post.php

<?php

$term = 'Some Term Name'
$taxonomy = 'some-taxonomy';

if ( function_exists( '\wpcom_vip_term_exists' ) ) {
  $term_data = \wpcom_vip_term_exists( $term, $taxonomy );
} else {
  $term_data = term_exists( $term, $taxonomy ); // phpcs:ignore
}

if ( ! is_array( $term_data ) ) {
  $term_data = wp_insert_term( $term, $taxonomy );
}

wp_set_post_terms( $post_id, $term_data['term_id'], $taxonomy );