<?php
//custom search
function __search_by_title_only( $search, &$wp_query ){
    global $wpdb;
    if ( empty( $search ) )
        return $search;
    $q = $wp_query->query_vars;
    $n = ! empty( $q['exact'] ) ? '' : '%';
    $search =
        $searchand = '';
    foreach ( (array) $q['search_terms'] as $term ) {
        $term = esc_sql( $wpdb->esc_like( $term ) );
        $search .= "{$searchand}($wpdb->posts.post_title LIKE '{$n}{$term}{$n}')";
        $searchand = ' AND ';
    }
    if ( ! empty( $search ) ) {
        $search = " AND ({$search}) ";
        if ( ! is_user_logged_in() )
            $search .= " AND ($wpdb->posts.post_password = '') ";
    }
    return $search;
}
add_filter( 'posts_search', '__search_by_title_only', 500, 2 );

function ajax_search(){
    extract($_POST);
    $allsearch = new WP_Query("s=".$key."&showposts=-1&post_type=any&post_status=publish");
    if($allsearch->have_posts()): while($allsearch->have_posts()) : $allsearch->the_post();
    global $post; ?>
    <p class="cfx">
        <a href="<?php the_permalink(); ?>">
            <?php if( has_post_thumbnail() ) the_post_thumbnail('thumbnail'); ?>
            <span><?php the_title(); ?></span>
        </a>
    </p>
    <?php endwhile; else :
    echo '<mark>There were no search results. <br />Please try using more general terms to get more results.</mark>';
    endif;
    exit();
}
add_action('wp_ajax_ajax_search', 'ajax_search');
add_action('wp_ajax_nopriv_ajax_search', 'ajax_search');