10. Validation Filters

add_filter( 'formforge_sanitize_field', function( $value, $field ) {
    // Force uppercase for a postal code field
    if ( ( $field['id'] ?? '' ) === 'field_zipcode' ) {
        return strtoupper( trim( $value ) );
    }
    return $value;
}, 10, 2 );

add_action( 'formforge_before_submit', function( $form_id, $data, $form ) {
    if ( $form_id !== 5 ) return;

    $allowed_domains = [ 'company.com', 'partner.org' ];
    foreach ( $data as $field_id => $field ) {
        if ( ( $field['type'] ?? '' ) !== 'email' ) continue;

        $domain = substr( strrchr( $field['value'], '@' ), 1 );
        if ( ! in_array( $domain, $allowed_domains, true ) ) {
            wp_send_json_error( [
                'message' => 'Only company email addresses are accepted.',
                'errors'  => [ $field_id => 'Please use your company email.' ],
            ] );
        }
    }
}, 10, 3 );

add_action( 'formforge_before_submit', function( $form_id, $data, $form ) {
    foreach ( $data as $field_id => $field ) {
        if ( ( $field['type'] ?? '' ) !== 'phone' ) continue;
        $phone = preg_replace( '/[^0-9+]/', '', $field['value'] );
        if ( strlen( $phone ) < 10 || strlen( $phone ) > 15 ) {
            wp_send_json_error( [
                'message' => 'Please provide a valid phone number.',
                'errors'  => [ $field_id => 'Phone must be 10-15 digits.' ],
            ] );
        }
    }
}, 10, 3 );