This snippet auto-appends an asterisk to the placeholder text of required fields in Gravity Forms. It ensures that only fields with placeholders are modified, and prevents double-adding asterisks.

gravity-forms-placeholder-asterisk.php

<?php
function gw_required_placeholder_asterisk( $form ) {
    foreach ( $form['fields'] as &$field ) {
        // Skip fields that don't support placeholders
        if ( ! is_callable( [ $field, 'get_entry_inputs' ] ) ) {
            continue;
        }

        // Single input fields
        if ( is_array( $field->inputs ) ) {
            $inputs = $field->inputs;
            foreach ( $inputs as &$input ) {
                if ( $field->isRequired && isset( $input['placeholder'] ) ) {
                    $input['placeholder'] = gw_append_asterisk( $input['placeholder'] );
                }
            }
            $field->inputs = $inputs;
        } else {
            if ( $field->isRequired && isset( $field->placeholder ) ) {
                $field->placeholder = gw_append_asterisk( $field->placeholder );
            }
        }
    }
    return $form;
}

function gw_append_asterisk( $text ) {
    // Avoid double-adding an asterisk
    if ( substr( $text, -1 ) !== '*' ) {
        $text .= ' *';
    }
    return $text;
}