WordPress Taxonomy Dropdown Functions

taxonomy-dropdown-functions.php

<?php

/**
 * Get tools, filtered by the taxonomy term, if one was selected.
 *
 * @return WP_Query Tools in the taxonomy term if one was selected, else all.
 */
function km_get_tools_in_taxonomy_term() {

	return new WP_Query( array(
			'post_type'      => 'tool', // Change this to the slug of your post type.
			'posts_per_page' => 500, // Display a maximum of 500 options in the dropdown.
			'tax_query'      => km_get_tools_in_taxonomy_term_tax_query(),
	) );

}


/**
 * Get the taxonomy query to be used by km_get_tools_in_taxonomy_term().
 *
 * @return array The taxonomy query if a term was selected, else an empty array.
 */
function km_get_tools_in_taxonomy_term_tax_query() {

	$selected_term = km_get_selected_taxonomy_dropdown_term();

	// If a term has been selected, use that in the taxonomy query.
	if ( $selected_term ) {
		return array(
			array(
				'taxonomy' => 'tools', // Change this to the slug of your taxonomy.
				'field'    => 'term_id',
				'terms'    => $selected_term,
			),
		);
	}

	// Otherwise, don't filter based on a taxonomy term and just get all the results.
	return array();
}


/**
 * Get the selected taxonomy dropdown term slug.
 *
 * @return string The selected taxonomy dropdown term ID, else empty string.
 */
function km_get_selected_taxonomy_dropdown_term() {
	return isset( $_GET[ 'tools' ] ) && $_GET[ 'tools' ] ? sanitize_text_field( $_GET[ 'tools' ] ) : '';
}