Multi Step form validation

Hello,

first, thank your for the great Plugin.

I want to switch from an existing form to a Multistep-Form. Maybe you can help me with field validation. I cannot find something in the documentation.

With the “normal” ACF-Plugin, I had a function checking if the phone number has at least 11 characters.
How can I do the same with your Plugin when clicking on the next step button?

*add_filter(‘acf/validate_value/key=field_5ff08e81392c5’, ‘my_acf_validate_value’, 10, 4);**
****
**function my_acf_validate_value( $valid, $value, $field, $input ){**
** if( !$valid ) {**
** return $valid; **
** }**
**
** $my_text_field = $_POST[‘acf’][‘field_5ff08e81392c5’];**
****
** if ( strlen($my_text_field) < 11 ) { **
** $valid = ‘Tel.Nr. is too short!’;**
** } **
** return $valid; **
**}*