proxy.php

<?php
/*--------------------------------------------------------------/
| PROXY.PHP                                                     |
| Created By: Évelyne Lachance                                  |
| Contact: eslachance@gmail.com                                 |
| Description: This proxy does a POST or GET request from any   |
|         page on the authorized domain to the defined URL      |
/--------------------------------------------------------------*/

// Destination URL: Where this proxy leads to.
$destinationURL = 'http://www.otherdomain.com/backend.php';

// The only domain from which requests are authorized.
$RequestDomain = 'mydomain.com';

// That's it for configuration!

if(!function_exists('apache_request_headers')) {
// Function is from: http://www.electrictoolbox.com/php-get-headers-sent-from-browser/
    function apache_request_headers() {
        $headers = array();
        foreach($_SERVER as $key => $value) {
            if(substr($key, 0, 5) == 'HTTP_') {
                $headers[str_replace(' ', '-', ucwords(str_replace('_', ' ', strtolower(substr($key, 5)))))] = $value;
            }
        }
        return $headers;
    }
}

// Figure out requester's IP to shipt it to X-Forwarded-For
$ip = '';
if (!empty($_SERVER['HTTP_CLIENT_IP'])) { 
    $ip = $_SERVER['HTTP_CLIENT_IP'];
    //echo "HTTP_CLIENT_IP: ".$ip;
} elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
    $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
    //echo "HTTP_X_FORWARDED_FOR: ".$ip;
} else {
    $ip = $_SERVER['REMOTE_ADDR'];
    //echo "REMOTE_ADDR: ".$ip;
}

preg_match('@^(?:http://)?([^/]+)@i', $_SERVER['HTTP_REFERER'], $matches);
$host = $matches[1];
preg_match('/[^.]+\.[^.]+$/', $host, $matches);
$domainName = "{$matches[0]}";

if($domainName == $RequestDomain) {

    $method = $_SERVER['REQUEST_METHOD'];
    $response = proxy_request($destinationURL, ($method == "GET" ? $_GET : $_POST), $method);
    $headerArray = explode("\r\n", $response[header]);

    foreach($headerArray as $headerLine) {
     header($headerLine);
    }
    echo $response[content];
 
  } else {

    echo "HTTP Referer is not recognized. Cancelling all actions";

  }

function proxy_request($url, $data, $method) {
// Based on post_request from http://www.jonasjohn.de/snippets/php/post-request.htm
    global $ip;
    // Convert the data array into URL Parameters like a=b&foo=bar etc.
    $data = http_build_query($data);
    $datalength = strlen($data);
 
    // parse the given URL
    $url = parse_url($url);
 
    if ($url['scheme'] != 'http') { 
        die('Error: Only HTTP request are supported !');
    }
 
    // extract host and path:
    $host = $url['host'];
    $path = $url['path'];
    
    // open a socket connection on port 80 - timeout: 30 sec
    $fp = fsockopen($host, 80, $errno, $errstr, 30);
 
    if ($fp){
        // send the request headers:
        if($method == "POST") {
            fputs($fp, "POST $path HTTP/1.1\r\n");
        } else {
            fputs($fp, "GET $path?$data HTTP/1.1\r\n");
        }
        fputs($fp, "Host: $host\r\n");
        
        fputs($fp, "X-Forwarded-For: $ip\r\n");
        fputs($fp, "Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\n"); 
        
           $requestHeaders = apache_request_headers();
        while ((list($header, $value) = each($requestHeaders))) {
            if($header == "Content-Length") {
                fputs($fp, "Content-Length: $datalength\r\n");
            } else if($header !== "Connection" && $header !== "Host" && $header !== "Content-length") {
                fputs($fp, "$header: $value\r\n");
            }
        }
        fputs($fp, "Connection: close\r\n\r\n");
        fputs($fp, $data);
 
        $result = ''; 
        while(!feof($fp)) {
            // receive the results of the request
            $result .= fgets($fp, 128);
        }
    }
    else { 
        return array(
            'status' => 'err', 
            'error' => "$errstr ($errno)"
        );
    }
 
    // close the socket connection:
    fclose($fp);
 
    // split the result header from the content
    $result = explode("\r\n\r\n", $result, 2);
 
    $header = isset($result[0]) ? $result[0] : '';
    $content = isset($result[1]) ? $result[1] : '';
 
    // return as structured array:
    return array(
        'status' => 'ok',
        'header' => $header,
        'content' => $content
    );
}

?>