Update post meta after successful payment with Gravity Forms

<?php
/**
 * Update ACF meta after successful payment
 *
 * @link https://docs.gravityforms.com/gform_post_payment_completed/
 *
 */
add_action( 'gform_post_payment_completed', 'wd_gform_submission_updates', 10, 2 );
function wd_gform_submission_updates( $entry, $payment_id ) {

	// Get form title of form that was submitted.
	$form = GFAPI::get_form( $entry['form_id'] );
	$form_title = $form['title'];

	// Update based on form title (can also use form ID)
	if( $form_title == 'Name of Form' ) {

		// Get form data.
		$form_sub_id     = (int) rgar( $entry, '1' ); // ID to update (int)
		$form_field_1    = rgar( $entry, '2' );

		// Update availability and reserved for fields.
		if ( ! empty( $form_sub_id ) ) {
			update_field( 'field_key', 'value', $form_sub_id );

			// Flush out page cache to show proper status (WP Rocket).
			if ( function_exists( 'rocket_clean_post' ) ) {
				rocket_clean_post( $form_sub_id );
			}
		}
	}
}