I need an array of custom taxonomy slugs. In the front-end, I get it using get_terms():

$tax_slugs = get_terms( 'course', array( 'fields' => 'slugs', 'parent' => 0, 'hide_empty' => 0 ));

result: Array ( [0] => breakfast [1] => lunch [2] => dinner [3] => dessert ) 

In the admin, the "Invalid Taxonomy" error will be raised by the function get_terms() because I've registered my taxonomy on the init action hook.

I need a function with SQL query and prepare method, to get an array of custom taxonomy slugs, like the one obtained with get_terms()

  • Is there a reason you need them before the init hook? Sep 18, 2017 at 8:11
  • I need it to create a theme option to sort the posts by taxonomy.
    – Giorgia
    Sep 18, 2017 at 11:28
  • That doesn't explain why you can't do it after the init hook. Where you creating theme options? Sep 18, 2017 at 11:37
  • I'm using Redux Framework to create theme options and I always get "Invalid Taxonomy" error in the backend, except with SQL query
    – Giorgia
    Sep 18, 2017 at 11:58

1 Answer 1

global $wpdb;

$slugs = $wpdb->get_col(
        $wpdb->term_taxonomy ON
            $wpdb->terms.term_id = $wpdb->term_taxonomy.term_id
        $wpdb->term_taxonomy.taxonomy = 'course'"

That will return an array of strings representing the taxonomy term slugs for terms in the course taxonomy.

  • Thank you Jacob! Is it possible to select only parent terms and exclude empty ones?
    – Giorgia
    Sep 18, 2017 at 11:29
  • Yeah it's possible, you just need to modify the query to look at those columns. Term parents and counts are in the term_taxonomy table, so you'd add AND $wpdb->term_taxonomy.parent = 0 AND $wpdb->term_taxonomy.count > 0 to the WHERE clause. Sep 18, 2017 at 11:38

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