Print category tree

Asset.php

foreach( get_categories('hide_empty=1') as $cat ) :
			if( !$cat->parent ) {
				echo '<ul><li><strong>' . $cat->name . '</strong></li>';
				process_cat_tree( $cat->term_id );
			}
		endforeach;
			
		wp_reset_query(); //to reset all trouble done to the original query
			//
		function process_cat_tree( $cat ) {
			
			$args = array('category__in' => array( $cat ), 'numberposts' => 1);
			$cat_posts = get_posts( $args );
			
			if( $cat_posts ) :
				foreach( $cat_posts as $post ) :
					echo '<li>';
					echo '<a href="' . get_permalink( $post->ID ) . '">' . $post->post_title . '</a>';
					echo '</li>';
				endforeach;
			endif;
			
			$next = get_categories('hide_empty=0&parent=' . $cat);
			
			if( $next ) :
				foreach( $next as $cat ) :
					echo '<ul><li><strong>' . $cat->name . '</strong></li>';
					process_cat_tree( $cat->term_id );
				endforeach;
			endif;
			
			echo '</ul>';
		}