Getting error while display html content on page - php

Question

I would like to display my website ads on other websites like google ads but I got error
Uncaught SyntaxError: Unexpected token < in JSON at position 0
I have used the codeigniter frame work and jquery, it is taking content as variable. Are there any possibilities to solve this issue?
This my Script code:
(window.jQuery || document.write("<script src=\"//ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js\"><\/script>"))
(function() {
var x = document.createElement("script");
x.type = "text/javascript";
x.async = true;
x.src = "http" + ("https:" == document.location.protocol ? "s" : "") + "://domain/ads/Ads/demo_ad";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(x, s)
})();
And My PHP code:
function demo_ad()
{
$ad_var = "<a href='http://www.example.com'><div style='position:absolute; width:560px; height:300px; z-index:10000;'><img width='600' height='200' src='http://www.w3schools.com/css/trolltunga.jpg'></div></a>";
echo $ad_var;
}

Answer 1

Here do this:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<script type="text/javascript">
(function()
{
var x = document.createElement("script");
x.type = "text/javascript";
x.async = true;
x.src = "http" + ("https:"==document.location.protocol?"s":"") + "://domain/ads/Ads/demo_ad";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(x, s)
})();
</script>
The PHP:
function demo_ad()
{
$ad_var = "<a href='http://www.aqua.deals'><div><img width='600' height='200' src='http://www.w3schools.com/css/trolltunga.jpg'></div></a>";
return $ad_var;
}
call to the funtion like this demo_ad()