limit WP search to titles only

wp-search-titles.php

<?php
add_filter ( 'posts_search', 'rkv_search_by_title_only', 500, 2	);
/**
 * restrict search query to only compare titles
 * @param  string	$search		search query passed by user
 * @param  mixed	$wp_query	global query from WP being modified
 * @return mixed			search results
 */
function rkv_search_by_title_only( $search, $wp_query ) {

	global $wpdb;
    	// skip processing - no search term in query
    	if ( empty( $search ) ) {
		return $search;
    	}	

	$q	= $wp_query->query_vars;
	$n	= ! empty( $q['exact'] ) ? '' : '%';

	$search	= '';
	$s_and	= '';

	foreach ( (array) $q['search_terms'] as $term ) :
		$term		= esc_sql( like_escape( $term ) );
		$search		.= "{$s_and}($wpdb->posts.post_title LIKE '{$n}{$term}{$n}')";
		$s_and		= ' AND ';
	endforeach;

	if ( ! empty( $search ) ) {
        	$search	= " AND ({$search}) ";
        	
        	if ( ! is_user_logged_in() ) {
            		$search	.= " AND ($wpdb->posts.post_password = '') ";
        	}	

	}

	return $search;
}