array (size=6)
      'location_cat' =>
        array (size=7)
          'deutschland' => string '-1' (length=2)
          'sachsen' => string '-1' (length=2)
          'thueringen' => string '-1' (length=2)
          'oesterreich' => string '-1' (length=2)
          'burgenland' => string '-1' (length=2)
          'kaernten' => string '-1' (length=2)
          'oberoesterreich' => string '-1' (length=2)

if ( strpos($term, '+') !== false ) {
	$terms = preg_split( '/[+]+/', $term );
	foreach ( $terms as $term ) {
		$tax_query[] = array_merge( $tax_query_defaults, array(
			'terms' => array( $term )
		) );
	}
} else {
	$tax_query[] = array_merge( $tax_query_defaults, array(
		'terms' => preg_split( '/[,]+/', $term )
	) );
}

<form role="search"
      method="get"
      id="searchform"
      action="<?php echo esc_url( home_url( '/' ) ); ?>">

	<?php
	// Contextual hook that takes the project_cat term into account
	do_action( $hook_name );
	?>

	<input type="hidden"
	       id="post_type"
	       name="post_type"
	       value="<?php echo get_query_var( get_queried_object()->taxonomy ); ?>"
			/>
	<input type="submit" id="searchsubmit" value="<?php esc_attr_e( 'Search' ); ?>" />
</form>

global $wpdb;
$result = $wpdb->get_col( "
	SELECT DISTINCT tt.taxonomy
	FROM {$wpdb->term_taxonomy} AS tt
" );

public function get_hierarchical()
{
	global $wpdb;
	$taxonomies = $wpdb->get_col( "
		SELECT DISTINCT tt.taxonomy
		FROM {$wpdb->term_taxonomy} AS tt
	" );
	$results = array();
	foreach ( $taxonomies as $tax )
	{
		false !== get_option( "{$tax}_children" )
			AND $results[] = $tax;
	}
	return $results;
}