Thanks! i solved my issue 🙂
This my code:
<?php
$services = get_field(‘servizi’);
?>
<div class=”tab services”>
<div><input <?php if( $services && in_array(‘value1’, $services) ) {
echo “checked”;}?> type=”checkbox” name=”servizi[]” value=”value1″ /> Value 1</div>
in my case so the user can modify his service AD from the custom form in the frontend and he finds the checkbox already selected to edit.