using file_get_contents() will only execute a simple GET query to retrieve the webpage.
Take a look at cURL in PHP: https://php.net/curl .
Example at php.net:
<?php
// create a new cURL resource
$ch = curl_init();
// set URL and other appropriate options
curl_setopt($ch, CURLOPT_URL, "http://www.example.com/");
curl_setopt($ch, CURLOPT_HEADER, 0);
// grab URL and pass it to the browser
curl_exec($ch);
// close cURL resource, and free up system resources
curl_close($ch);
?>
Using the curl_setopt function, with the CURL_COOKIE define, you can create your own Cookie: contents in the HTTP header.