GiveWP Custom field with validation

fields.php

/**
 * Add Custom Donation Form Fields
 *
 * @param $form_id
 */
function give_myprefix_custom_form_fields( $form_id ) {

    if ( $form_id == 8) {
        //$forms = array( 8 );
        ?>
        <div id="give-referral-wrap">
            <label class="give-label" for="give-referral"><?php _e( 'Triath-a-Toddlers Name?:', 'give' ); ?><span class="give-required-indicator">*</span>	<span class="give-tooltip icon icon-question" data-tooltip="<?php _e( 'Please tell us whom you are sponsoring.', 'give' ) ?>"></span>
            </label>
            <textarea class="give-textarea" name="give_referral" id="give-referral"></textarea>
        </div>
        <?php
    }
}

add_action( 'give_after_donation_levels', 'give_myprefix_custom_form_fields', 10, 1 );

/*
 * Validate Custom Field
 *
 * Check for errors without custom fields
 *
 * @param $valid_data
 * @param $data
 */
function give_myprefix_validate_custom_fields( $required_fields, $form_id ) {

    //$forms = array( 8 );

    if ( $form_id == 8 ) {
        $required_fields['give_referral'] = array(
            'error_id' => 'invalid_give_referral',
            'error_message' => __( 'Please tell us whom you are sponsoring.', 'give' ),
);
}

    return $required_fields;
}

add_filter( 'give_donation_form_required_fields', 'give_myprefix_validate_custom_fields', 10, 2 );