Admin search improvement to look in custom fields

woo-custom-field-admin-search.php

<?php 
//Improve admin custom search
function custom_search_query( $query ) {
    $custom_fields = array(
        // put all the meta fields you want to search for here
        'meta_field',
    );
    $searchterm = $query->query_vars['s'];

    // we have to remove the 's' parameter from the query, because it will prevent the posts from being found
    $query->query_vars['s'] = '';

    if ($searchterm != '') {
        $meta_query = array('relation' => 'OR');
        foreach($custom_fields as $cf) {
            array_push($meta_query, array(
                'key' => $cf,
                'value' => $searchterm,
                'compare' => 'LIKE'
            ));
        }
        $query->set('meta_query', $meta_query);
    };
}
add_filter( 'pre_get_posts', 'custom_search_query');