Filter Posts Search Admin WordPress - Custom Field

filter_custom_field_search_wordpress_admin.php

<?php
function my_admin_post_search_by_custom_fields( $query ) {
        if ( ! is_admin() ) {
                return;
        }
 
        // Search just for posts
        if ( isset( $query->query_vars['post_type'] ) && 'post' !== $query->query_vars['post_type'] ) {
                return;
        }
 
        if ( ! empty( $query->query_vars['s'] ) ) {
                $term          = $query->query_vars['s'];
                $custom_fields = array( 'my_custom_field' ); // Set here your custom fields for search
                $meta_query    = array( 'relation' => 'OR' );
 
                foreach ( $custom_fields as $field ) {
                        array_push( $meta_query, array(
                                'key'     => $field,
                                'value'   => $term,
                                'compare' => 'LIKE'
                        ) );
                }
 
                $query->set( 'meta_query', $meta_query );
 
                // Exclude regular search
                unset( $query->query_vars['s'] );
        }
}
 
add_filter( 'pre_get_posts', 'my_admin_post_search_by_custom_fields' );