PHP Import WP Terms child term into custom post type

Question

I have created a import tool to import data from a json file to create posts in my custom post type. It all works well and I can import acf fields as well as assigned terms. My question is, how can I import child term assigned to the term.

I have two variables right now that collects the data. I would like the have the variable eventCategoryChildName to assign its vaule as a child term to eventCategoryID

  $eventCategoryChildName = $ev['OfficialCity'];
  $eventCategoryId = $ev['RegionID'];

Here is how the import of terms functions right now without child terms:

 // set category terms
 $cat_ids = $eventCategoryName;
 // Add these categories, note the last argument is true.
 wp_set_object_terms( $post_id, $cat_ids, 'lan', true );

Edit:

So I managed to import the child associated to the right parents but they are not checked to the post

    // set category terms
    $cat_ids = $eventCategoryName;

    // Import category name
    $term_taxonomy_ids = wp_set_object_terms( $post_id, $cat_ids, 'lan', true );

    $parent_term = wp_set_object_terms( $post_id, $cat_ids, 'lan', true );

    // Check terms import for errors
    if ( is_wp_error( $term_taxonomy_ids ) ) {
        // There was an error somewhere and the terms couldn't be set.
        echo $return->get_error_message();
    } else {
        // Success! These categories were added to the post.
    }


    $parent_term = term_exists( $eventCategoryName, 'lan' ); 
    wp_insert_term(
      $eventCategoryChildName,                // Customize as you wish
      'lan',
      array(
          'parent'      => $parent_term['term_id'],
          'slug'        => $eventCategoryChildName  // Customize as you wish
      )
    );

    if ( !is_wp_error( $child_term_result ) ) {
      wp_set_object_terms( $post_id, $child_term_result['term_id'], 'lan', true );
  }

Answer 1

Firstly, you should check the result of wp_set_object_terms , to see if an error was returned:

$term_taxonomy_ids = wp_set_object_terms( $post_id, $cat_ids, 'lan', true );
if ( is_wp_error( $term_taxonomy_ids ) ) {
    // There was an error somewhere and the terms couldn't be set.
    echo $return->get_error_message();
} else {
    // Success! These categories were added to the post.
}

Then, the term you want to add may not exists. In such case, wp_set_object_terms will return an invalid_taxonomy error. So you may want to add such missing term to your taxonomy:

wp_insert_term(
    'Term Name',                      // Customize as you wish
    'lan',
    array(
        'description' => 'Term desc', // Customize as you wish
        'slug'        => 'lan-slug1'  // Customize as you wish
    )
);

// For child term:
$parent_term = term_exists( 'parent_term_id', 'lan' );
$child_term_result = wp_insert_term(
    'Child Term Name',                // Customize as you wish
    'lan',
    array(
        'parent'      => $parent_term['term_id']
        'description' => 'Term desc', // Customize as you wish
        'slug'        => 'lan-slug1'  // Customize as you wish
    )
);

// Add the child term to the post
if ( !is_wp_error( $child_term_result ) ) {
     wp_set_object_terms( $post_id, $child_term_result['term_id'], 'lan', true );
}

Finally, be sure you execute this code after -at least- the init hook of Wordpress. For instance:

function parse_my_json() {
    // Your code here
}
add_action('init','parse_my_json');

Useful references:

• https://codex.wordpress.org/Function_Reference/wp_set_object_terms
• https://codex.wordpress.org/Class_Reference/WP_Error
• https://codex.wordpress.org/Function_Reference/wp_insert_term