In an attempt to make your WordPress search even more user friendly, you can highlight the search terms in the results. We did this for one of our clients, so we thought it would be useful for other users. In this article we will show you how you can highlight search terms in the results in WordPress.
First open your search.php and look for the following code:
<?php the_title(); ?>
Replace the above code with:
<?php echo $title; ?>
Make sure that you paste this line above the title code:
<?php $title = get_the_title(); $keys= explode(" ",$s); $title = preg_replace('/('.implode('|', $keys) .')/iu', '<strong class="search-excerpt">\0</strong>', $title); ?>
Now open your CSS file and add the styling for the class search-excerpt, and it will highlight the term. Currently the code is making the search terms bold.
Source: Michael Martin