<?php

function ajax_search() {
    $search_keyword = $_POST['query'];
    $data = array();

    if (!empty($search_keyword)) {
        $query = new WP_Query(array(
            'post_type' => 'post',
            'posts_per_page' => 5,
            's' => $search_keyword,
        ));

        if ($query->have_posts()) {
            while ($query->have_posts()) {
                $query->the_post();
                $data[] = array(
                    'title' => get_the_title(),
                    'link' => get_permalink(),
                );
            }
        }
    }

    wp_send_json($data);
    wp_die();
}

add_action('wp_ajax_ajax_search', 'ajax_search');
add_action('wp_ajax_nopriv_ajax_search', 'ajax_search');