Because this is running through the CLI there's no real way for the script to know the correct domain to generate an absolute URI.
I ended up creating a view helper at module/Application/src/Application/View/Helper/CliDomain.php
<?php
namespace Application\View\Helper;
use Zend\View\Helper\AbstractHelper;
class CliDomain extends AbstractHelper {
protected $_config_protocol;
protected $_config_domain;
public function __construct(array $cliConfig) {
$this->_config_protocol = $cliConfig['scheme'];
$this->_config_domain = $cliConfig['domain'];
}
public function __invoke() {
return $this->_config_protocol.'://'.$this->_config_domain;
}
}
and configured the factory in module/Application/config/module.config.php
return array(
...
'view_helpers' => array(
...
'cliDomain' => function ($sm) {
$config = $sm->getServiceLocator()->get('config');
if (!isset($config['cli_url'])) {
throw new \InvalidArgumentException('Please add a "cli_url" configuration to your project in order for cron tasks to generate emails with absolute URIs');
}
return new \Application\View\Helper\CliDomain($config['cli_url']);
},
and in the project's config/autoload/global.php file I added a new key to the returned array
<?php
return array(
...
'cli_config' => array(
'scheme' => 'http',
'domain' => 'prod.example.com',
),
);
for the staging server I added a matching config entry in config/autoload/local.php
<?php
return array(
...
'cli_config' => array(
'scheme' => 'http',
'domain' => 'staging.example.com',
),
);
So in the question's view script I just prepended a call to the helper in the URL and don't bother forcing canonical.
<a href="<?php echo $this->cliDomain() . $this->url('some-route'); ?>">a link!</a>