This question has been answered by multiple community members. See the first response.
$usernameField = $this->modx->getOption('usernameField', $scriptProperties, 'username'); $username = $hook->getValue($usernameField); $user = $modx->getObject('modUser', array('username' => $username)); if ($user) { $userId = $user->get('id'); $profile = $modx->getObject('modUserProfile', array('internalKey' => $userId)); if ($profile) { $fullName = $profile->get('fullname'); $modx->setPlaceholder('fullname', $fullName); } } return true;
&postHooks=`FullName` &preHooks=`FullName`
[[+fullname]]