Laravel: How to print out strings in an array within escaped controller text

I am setting a text block to email out and setting the $body variable. The issue is that my $app->reference_image_url field is an array of strings so I get an array to string conversion error. I tried a foreach loop to have each url string added but that threw an error.

       $body = <<<COMMENT
* Main Image
$app->image_url
$app->image_notes

* Reference Images

$app->reference_image_url
$app->reference_image_notes
COMMENT;

$this->send($body);

via Chebli Mohamed