Question is simply easy, but it seems I can't find solution so..
I'm getting html string from file using:
ob_start();
require_once 'view/form.php';
$html = ob_get_contents();
ob_end_clean();
And it works, then I'm putting this string in text box using
echo '<br /><textarea style="width:100%" rows="10">'.$html.'</textarea>';
But html goes out messy with lots of white spaces and tabs, is there a way to format it in decent way to be more readable?