Unexpected percent encoding of POST data may yield wrong Content-Length

[avbentem]

It seems that $_POST and http_build_query are not symmetrical. Currently, $_POST is tried first when reading the original POST request:

} elseif ('POST' == $request_method) {
    $request_params = $_POST;
    if (empty($request_params)) {
        $data = file_get_contents('php://input');
        if (!empty($data)) {
            $request_params = $data;
        }
    }
} elseif ('PUT' == $request_method || 'DELETE' == $request_method) {
    $request_params = file_get_contents('php://input');
} else {
    $request_params = null;
}

And if $_POST gets some content above, then http_build_query is used when passing the request to the remote server:

// add data for POST, PUT or DELETE requests
if ('POST' == $request_method) {
    $post_data = is_array($request_params) ? http_build_query($request_params) : $request_params;
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS,  $post_data);
} elseif ('PUT' == $request_method || 'DELETE' == $request_method) {
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, $request_method);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $request_params);
}

Note that $_POST percent decodes if needed, but http_build_query percent encodes whenever possible.

For example, consider Content-Type: application/x-www-form-urlencoded with a POST body including an @ that (erroneously) is not percent-encoded:

user=me@example.com&password=sEcr3t

Here, $_POST['user'] will simply return the original value as decoding is not needed: me@example.com. However, http_build_query will encode the @ to read %40. And the original Content-Length header will not be increased to make up for the two extra characters. Hence, the remote server may get a truncated body.

I'm not using PHP a lot, but I'd be tempted to avoid any parsing that $_POST does, and always use php://input. However:

php://input is not available with enctype="multipart/form-data"

So maybe something like the following would be better?

} elseif ('POST' == $request_method) {
    $data = file_get_contents('php://input');
    if (!empty($data)) {
        $request_params = $data;
    }
    else {
        $request_params = $_POST;
    }

(This works for me, but I have not tested with enctype="multipart/form-data".)