PHP: Fetch remote page AFTER JS events have loaded - php

Question

I'm using a simple method of loading a remote webpage that works fine mostly:
$output = file_get_contents($item['URL']);
$html->loadHTML($output);
After which I can search for tags by type or name or ID, but the problem is that the main content I want is generated after the fact by JS in the last second. When loading in a browser, you don't notice it, but when trying to get it with file_get_contents, I get the page as it exists before the last minute JS runs.
Here's the partial code that loads what I want so you can see what I mean, but it's pretty straighforward: the page I get isn't the "complete" page.
<script type="text/javascript">ImageMachine.prototype.ImageMachine_Generate_Thumbnail = function (thumbnail_image, main_image, closeup_image, type_code) {
var thumbnail,
img;
I tried using CURL too, but no luck.
$header[] = "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,;q=0.8";
$header[] = "Connection: keep-alive";
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $item['URL']);
curl_setopt($ch, CURLOPT_HTTPHEADER, $header_str);
// curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_COOKIE, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
// curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_ENCODING, '');
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_USERAGENT, $this_time);
$output = curl_exec($ch);
curl_close($ch);
#$html->loadHTML($output);
Is there a way to get the whole thing? I want the same page a browser or user would see if they load the page.