Get the date of the last payment on a gravity PDF invoice

gravity-pdf-date.php

<?php

// Used within a PDF template
// [...]

$invoice_date = date( $date_format, strtotime( $form_data['misc']['date_time'] ) );

// Fetch last payment date in database
global $wpdb;
$last_payment_date = $wpdb->get_var( $wpdb->prepare( "SELECT date_created FROM {$wpdb->prefix}gf_addon_payment_transaction WHERE lead_id=%d ORDER BY date_created DESC", $entry['id'] ) );
$formatted_last_payment_date = date( $date_format, strtotime( $last_payment_date ) );

$invoice_date = $invoice_date;
if ( $last_payment_date > $form_data['misc']['date_time'] ) {
    $invoice_date = $formatted_last_payment_date;
}