How to add image posting to my PHP script?

[oauthlibrary]

I’m trying to post a message with an image to Twitter through PHP and cURL. It’s working for the message but I don’t know how to add the image to it.

From the documentation:

Unlike POST statuses/update, this method expects raw multipart data. Your POST request's Content-Type should be set to multipart/form-data with the media[] parameter

This is the PHP:

<?php
class Tweet {
public $url = 'https://api.twitter.com/1.1/statuses/update_with_media.json';

function the_nonce(){
    $nonce = base64_encode(uniqid());
    $nonce = preg_replace('~[\W]~','',$nonce);
    return $nonce;
}

function get_DST($status){

    $url = $this->url;

    $consumer_key = "";
    $nonce = $this->the_nonce();
    $sig_method = 'HMAC-SHA1';
    $timestamp = time();
    $version = "1.0";
   $token = "";
    $access_secret = "";
    $consumer_secret =  "";

    $param_string = 'oauth_consumer_key='.$consumer_key.
            '&oauth_nonce='.$nonce.
            '&oauth_signature_method='.$sig_method.
            '&oauth_timestamp='.$timestamp.
            '&oauth_token='.$token.
            '&oauth_version='.$version.
            '&status='.rawurlencode($status);
    $sig_base_string = 'POST&'.rawurlencode($url).'&'.rawurlencode($param_string);
    $sig_key = rawurlencode($consumer_secret).'&'.rawurlencode($access_secret);

    $tweet_sig = base64_encode(hash_hmac('sha1', $sig_base_string, $sig_key, true));

    $DST = 'OAuth oauth_consumer_key="'.rawurlencode($consumer_key).'",'.
        'oauth_nonce="'.rawurlencode($nonce).'",'.
        'oauth_signature="'.rawurlencode($tweet_sig).'",'.
        'oauth_signature_method="HMAC-SHA1",'.
        'oauth_timestamp="'.rawurlencode($timestamp).'",'.
        'oauth_token="'.rawurlencode($token).'",'.
        'oauth_version="1.0"';
    return $DST;
}

function set($status){
$url = $this->url;
$ch = curl_init();

curl_setopt($ch, CURLOPT_HTTPHEADER, array('Authorization: ' . $this->get_DST($status)));
curl_setopt($ch, CURLOPT_VERBOSE, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, 'status='.rawurlencode($status));
curl_setopt($ch, CURLOPT_URL, $url);
$result = json_decode(curl_exec($ch));
$resultString =  print_r($result,true);;
curl_close($ch);
}

$status->set("hello");
?>

How to add the media[] part to it?