Highlight current page on sidebar's menu list

Hi! I know that if I’ll use <?php wp_list_pages(); ?> that I’ll have a current_page_item class. But I also need to display a custom field value called “category” so I opted not to use wp_list_pages.

Anyway, I added a menu list on my sidebar where it features the child pages for let say “Articles”. I would to be able to highlight the “active page” on the menu list. I was thinking of adding some variable like $current_page = so I can add a class and use that in my CSS. I just don’t know where I should put it. Also I’m not using sidebar widgets – if that’s a useful information for you guys.

I’m a little new in WordPress.

Here is the code I used:

<div class="posts">
	<?php
	 $parent_id = get_post(44);

	$args = array(
	'post_type' => 'page',
	'posts_per_page' => -1,
	'post_parent' => $parent_id->ID,
	'order' => 'ASC',
	'orderby' => 'menu_order'
	);

	$parent = new WP_Query ( $args );

	if ($parent->have_posts () ) :
        ?>

       <ul>

	  <?php while ($parent->have_posts()): $parent->the_post(); ?>

                  <a href="<?php the_permalink(); ?>">
			 <li>
				 <h4><?php the_title(); ?></h4>
				 <h6><?php echo get_post_meta($post->ID, "category", true); ?></h6>
			 </li>
		 </a>

	 <?php endwhile; ?>

	<?php endif; wp_reset_query(); ?>	

      </ul>
</div>

Thank you in advance!