Simple PHP image proxy

proxy.php

<?php

$PROXY = 'https://yourdomain.top/proxy.php?url=';

# This script forwards the call

# Check for url parameter, and prevent file transfer
if (isset($_GET['url']) and preg_match('#^https?://#', $_GET['url']) === 1) {
    $url .= $_GET['url'];
} else {
    header('HTTP/1.1 404 Not Found');
    exit;
}

# Check if the client already has the requested item
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) or 
    isset($_SERVER['HTTP_IF_NONE_MATCH'])) {
    header('HTTP/1.1 304 Not Modified');
    exit;
}

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_USERAGENT, 'Searsia/1.0');
curl_setopt($ch, CURLOPT_BINARYTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 4);
curl_setopt($ch, CURLOPT_BUFFERSIZE, 12800);
curl_setopt($ch, CURLOPT_NOPROGRESS, false);
curl_setopt($ch, CURLOPT_PROGRESSFUNCTION, function($DownloadSize, $Downloaded, $UploadSize, $Uploaded) { return ($Downloaded > 1024 * 512) ? 1 : 0; } ); # max 500kb
$out = curl_exec ($ch);
curl_close ($ch);

$file_array = explode("\r\n\r\n", $out, 2);
$header_array = explode("\r\n", $file_array[0]);
foreach($header_array as $header_value) {
    $header_pieces = explode(': ', $header_value);
    if(count($header_pieces) == 2) {
        $headers[$header_pieces[0]] = trim($header_pieces[1]);
    }
}
if (array_key_exists('Location', $headers)) {
    $newurl = urlencode($headers['Location']);
    header("HTTP/1.1 301 Moved Permanently"); 
    header('Location: ' . $PROXY . $newurl);
} else {
    if (array_key_exists('Content-Type', $headers)) {
        $ct = $headers['Content-Type'];
        if (preg_match('#image/png|image/.*icon|image/jpe?g|image/gif#', $ct) !== 1) {
            header('HTTP/1.1 404 Not Found');
            exit;
        }
        header('Content-Type: ' . $ct);
    }
    if (array_key_exists('Content-Length', $headers))
        header('Content-Length: ' . $headers['Content-Length']);
    if (array_key_exists('Expires', $headers))
        header('Expires: ' . $headers['Expires']);
    if (array_key_exists('Cache-Control', $headers))
        header('Cache-Control: ' . $headers['Cache-Control']);
    if (array_key_exists('Last-Modified', $headers))
        header('Last-Modified: ' . $headers['Last-Modified']);
    echo $file_array[1];
}
?>

Many thanks for script!

I have some suggestions to improve script:

• $header_array = explode("\n", $header_blocks[array_key_last($header_blocks)]); change to $header_array = explode("\n", array_pop($header_blocks)); since array_key_last() is only supported in PHP 7 and higher.

• you did strtolower($header_pieces[0]) and then uses if (array_key_exists('Expires', $headers)) in upper case. Its need to be changed to lowercase.

• add the WEBP and SVG image types: if (preg_match('#image/png|image/.*icon|image/jpe?g|image/gif|image/webp|image/svg\+xml#', strtolower($ct)) !== 1) {, and you don't need strtolower there since all $headers[] already have lowercase.

• the $header_pieces = explode(': ', $header_value); change ': ' to ':' (without trailing space). It can help to handle some wrong headers. Anyway you do trim() after.

• add the curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36'); to set useragent otherwise something like curl/7.29.0 will be used by default and a lot of hostings treat it as bot (an ban it).

• its heplful to add CURLOPT_SSL_VERIFYPEER and CURLOPT_SSL_VERIFYHOST options to avoid SSL problems with some hostings:

  $version = curl_version();
  if ($version !==FALSE && ($version['features'] & CURL_VERSION_SSL)) { // Curl do support SSL
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
  curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
  }

Thanks @egranty I have updated my comment :)

That's really helpful, thanks both!

This works!