httpProxy.php

function httpProxy($request, $upstream, Closure $callback = null)
{
    $requestHeaders = $request['headers'];
    unset($requestHeaders['Host'], $requestHeaders['Connection']);
    $requestHeaders = stringifyHeaderPairs($requestHeaders);
    $ch = curl_init($upstream . $request['uri']);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_VERBOSE, 1);
    curl_setopt($ch, CURLOPT_HEADER, 1);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, $request['method']);
    if ($request['method'] === 'POST') {
        curl_setopt($ch, CURLOPT_POSTFIELDS, file_get_contents($request['contentsFile']));
    }
    curl_setopt($ch, CURLOPT_HTTPHEADER, $requestHeaders);
    $response = curl_exec($ch);
    $responseHeadersSize = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
    $responseHeaders = substr($response, 0, $responseHeadersSize);
    $headers = array_filter(explode("\r\n", $responseHeaders));
    $body = substr($response, $responseHeadersSize);
    if ($callback) {
        list ($body, $headers) = $callback($body, $headers);
    }
    $headerPairs = headerPairs($headers);
    unset($headerPairs['Transfer-Encoding']);
    foreach (stringifyHeaderPairs($headerPairs) as $header) {
        header($header, true);
    }
    echo $body;
}

function headerPairs($headers)
{
    $headerPairs = [];
    foreach ($headers as $i => $header) {
        $pair = explode(': ', $header, 2);
        if (count($pair) === 1) {
            array_unshift($pair, $i);
        }
        $headerPairs[$pair[0]] = $pair[1];
    }
    return $headerPairs;
}

function stringifyHeaderPairs($headers)
{
    array_walk($headers, function (&$value, $key) {
        $value = is_int($key) ? $value : "$key: $value";
    });
    $headers = array_values($headers);
    return $headers;
}