But... I suspect that you'll just use this iframe once per page. Rigging up some ajax for a once-per-page thing is probably a little overkill.
So, at the top of your page, you could do something like any of these:
ObjectYoureWorkingWith.Title = '<?php echo $the_title(); ?>';
var TitleObjectList = <?php echo json_encode($list_of_titles); ?>;
I was typing the above on my cell (not the best way to respond to this sort of thing). Let me demonstrate what I'm describing:
Let's say in your php you have 20 titles you want to work with. You could make an associative array. Use an Id or whatever identifier you want to call it with.
$titleArray = [ 123 => 'Title1', 456 => 'Title2']; //(and so on....)
Then, on the php page you're wanting that data, do this:
var titleArray = <?php echo json_encode($titleArray); ?>;
This will now allow you to access it on that page (or in a js file loaded on that page) by doing this:
var myFirstTitle = titleArray["123"]; //This will return "Title1"