how to create a custom live search in WordPress from scratch

I am new in WordPress and I trying to create a live search using ajax, I want when a user presses a button a box appears, and search results show in that box. for doing this I created a folder in my theme folder called livesearch in that folder I put a file called search-live.php and the code in that file like this:

<?php
//echo $_GET['search'];
$test = GetMySearchResult($_GET['search']);
print_r($test);

and in my functions.php file I create a function called GetMySearchResult like this:

function GetMySearchResult($search){
    global $wpdb;
    $myrows = $wpdb->get_results( "SELECT * FROM wp_posts post_type = post ID LIKE %" . $search . "%" );
    
    return $myrows;
}
add_action('init', 'GetMySearchResult');

and I send data to search-live.php using ajax and code Like this:

<script>
        var GetSearch = document.getElementById('search');
         GetSearch.addEventListener("keyup", function(){
             //InfoData = {slug:GetSearch.value}
             $.ajax({
                type: "GET",
                url: '<?php echo get_site_url(); ?>/wp-content/themes/webranko/livesearch/search-live.php?search=' + GetSearch.value ,
                data: '',
                datatype: "html",
                success: function(result) {
                    console.log(result);
                }
            });
         });
            
         </script>

I already $_GET['search']; and everything it’s ok and I can see the result in my console but when I call GetMySearchResult($_GET['search']) it gives me a fatal error like this:

Fatal error: Uncaught Error: Call to undefined function GetMySearchResult() in C:xampphtdocswebwp-contentthemeswebrankolivesearchsearch-live.php:3 Stack trace: #0 {main} thrown in C:xampphtdocswebwp-contentthemeswebrankolivesearchsearch-live.php on line 3

what I missed or what I do wrong?

Answer

For creating live search just need send a GET request to wp-json no need to make a new query

just use this URL in ajax request:

<?php echo get_site_url(); ?>wp-json/wp/v2/posts?search=' + GetSearch.value 

So ajax code should be like this:

<script>
        var GetSearch = document.getElementById('search');
         GetSearch.addEventListener("keyup", function(){
             //InfoData = {slug:GetSearch.value}
             $.ajax({
                type: "GET",
                url: '<?php echo get_site_url(); ?>wp-json/wp/v2/posts?search=' + GetSearch.value ,
                data: '',
                datatype: "html",
                success: function(result) {
                    console.log(result);
                }
            });
         });
            
         </script>

and the HTML search input should be like this:

<input type="search" id="search" name="search" placeholder="search" autocomplete="off"/>

you must turn off the autocomplete of input