php curl with header modify

I am testing a flow where i need to spoof ip and mobile number to test. The problem is CURLOPT_HTTPHEADER. The header value i am sending is not accessible by the link. Below is my code.

<?php
    $cookie_file = '/tmp/checkcookie';
    $url = "https://example.com/someparameter=value";

    $ip = '10.18.25.123';
    $msisdn = '9878656565';

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_HTTPHEADER, array('X-Forwarded-For: $ip','MSISDN: $msisdn'));
    curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)");
    curl_setopt($ch, CURLOPT_COOKIEFILE, $cookie_file);
    curl_setopt($ch, CURLOPT_COOKIEJAR, $cookie_file);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_HEADER, 0);
    echo $response = curl_exec($ch);
?>

Any idea what to change. Thanks