get_terms returns empty array for parameter fields=names

[Sarky-de]

The function call

get_terms('post_tag', 'fields=names')

is expected to return an array containing all tag names. An empty array is returned instead.

get_terms('post_tag', 'fields=ids')

returns an array with all tag IDs as expected.

This error is the result of wrong operator and a missing if-condition in taxonomy.php:

Current code (starting from line 572:

	else if ( 'names' == $fields )
		$select_this == 't.name';

	$query = "SELECT $select_this FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy IN ($in_taxonomies) $where ORDER BY $orderby $order $number";

	if ( 'all' == $fields ) {
		$terms = $wpdb->get_results($query);
		update_term_cache($terms);
	} else if ( 'ids' == $fields ) {
		$terms = $wpdb->get_col($query);
	}

Fixed code:

	else if ( 'names' == $fields )
		$select_this = 't.name';

	$query = "SELECT $select_this FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy IN ($in_taxonomies) $where ORDER BY $orderby $order $number";

	if ( 'all' == $fields ) {
		$terms = $wpdb->get_results($query);
		update_term_cache($terms);
	} else if ( ('ids' == $fields) || ('names' == $fields) ) {
		$terms = $wpdb->get_col($query);
	}

[Sarky-de]

Patch file for ticket #5780

[ryan]

(In [6738]) Fix fields=names query in get_terms(). Props Sarky-de. fixes #5780