gistfile1.php

<?php

//TODO get URL from parameters and authenticate it with an expiring hash/timestamp
$url = 'http://traffic.libsyn.com/atpfm/atp95.mp3'; 


// Forward these headers from original request
$requestHeaders = [];
if (isset($_SERVER['HTTP_USER_AGENT'])) $requestHeaders[] = 'User-Agent: ' . $_SERVER['HTTP_USER_AGENT'];
if (isset($_SERVER['HTTP_RANGE']))      $requestHeaders[] = 'Range: ' . $_SERVER['HTTP_RANGE'];
if (isset($_SERVER['HTTP_REFERER']))    $requestHeaders[] = 'Referer: ' . $_SERVER['HTTP_REFERER'];
if (isset($_SERVER['HTTP_IF_NONE_MATCH'])) $requestHeaders[] = 'If-None-Match: ' . $_SERVER['HTTP_IF_NONE_MATCH'];
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']))    $requestHeaders[] = 'If-Modified-Since: ' . $_SERVER['HTTP_IF_MODIFIED_SINCE'];

// Forcibly add these (overwriting any previous values)
$requestHeaders[] = 'X-Forwarded-For: ' . $_SERVER['REMOTE_IP'];
$requestHeaders[] = 'X-Real-IP: ' . $_SERVER['REMOTE_IP'];

$isHeadRequest = $_SERVER['REQUEST_METHOD'] == 'HEAD';
$sentStatus = 0;
$c = curl_init($url);

curl_setopt_array($c, [
    CURLOPT_CONNECTTIMEOUT => 5,
    CURLOPT_TIMEOUT => 120,
    CURLOPT_PROTOCOLS => CURLPROTO_HTTP | CURLPROTO_HTTPS,
    CURLOPT_HTTPHEADER => $requestHeaders,
    CURLOPT_HEADERFUNCTION => function($c, $line) use ($sentStatus, $isHeadRequest) {
        if (! $sentStatus && ($sentStatus = curl_getinfo($c, CURLINFO_HTTP_CODE)) ) {
            http_response_code($sentStatus);
        }
        
        // In redirection, this function is called for every subrequest.
        // Only output headers if the most recent HTTP response is not a redirect,
        // or in response to a HEAD request that's not following redirects.
        if ($sentStatus &&
            ($isHeadRequest || ($sentStatus != 301 && $sentStatus != 302)) &&
            ! headers_sent()
        ) { header(trim($line)); }
        
        return strlen($line);
    }
]);

if ($isHeadRequest) {
    curl_setopt($c, CURLOPT_CUSTOMREQUEST, 'HEAD');
} else {
    curl_setopt_array($c, [
        CURLOPT_FOLLOWLOCATION => 1,
        CURLOPT_MAXREDIRS => 5,
        CURLOPT_REDIR_PROTOCOLS => CURLPROTO_HTTP | CURLPROTO_HTTPS,
    ]);
}

curl_exec($c); // streams output to stdout
curl_close($c);