conditional statement in heredoc

I have just been introduced to the heredoc method and am getting into it slowly.

I figured I could use conditional statements inside the heredoc syntax but Im running into some roadblocks - (mainly my lack of knowledge)

What Im trying to do is create a hr from an array - I can get the color and the style but when it comes to showing the result, I'm falling short.

If I run this by itself it works fine - it uses a checkbox called dashed_dashed_use and if its checked it runs this, and all is well - however. Im trying to use a ifelse statement inside to simply show a

---

if the checkbox is not "checked".

   // START HEREDOC OUTPUT STRING
     $output = <<< START

   START;
    // IF Yes Box HAS CONTENT - ADD TO OUTPUT
    // ELSE IGNORE
    if (!empty($dashed_dashed_use)) {
      $output .= <<< DD1
        <hr style="border: 2px dashed; color:{$dashed_dashed};" data-dashed_dashed="{$dashed_dashed}">
    DD1;
    }

    // ADD CLOSING TAGS TO OUTPUT
       $output .= <<< OUTPUT_FINAL
     OUTPUT_FINAL;
    return $output;
    }

I cant just have a hr after the START as it will always show. So I need it so that it's a regular hr unless DD1 has been activated by the checkbox - (there are more varieties of the same, but I figured I would be able to replicate a single working version and just change the names of the $ fields.

Is this pretty straightforward, or do I need to code copies for every instance of hr I have.