View source for How to populate coupon code on signup page from PHP session

Add this code to [[site.php file]]:
<source>
if (!isset($_SESSION['amember']['_signup_container'])) {
    $_SESSION['amember']['_signup_container'] = array(
        'datasources' => array(),
        'values' => array(),
        'valid' => array(),
        'opaque' => array()
    );
}
$_SESSION['amember']['_signup_container']['values']['page-0']['coupon'] = 'TEST';
</source>
You can replace TEST with your actual coupon code.