Custom set of photo sizes, cURL and PHP

What is the correct way to get customized photo sizes with php?

$acs_app_key = '';
 
  $data = array(
    'title' => $post_title,
    'content' => $post_content,
    'photo' => '@header.jpg',
    //'photo_sizes[android]' => '480x225',
    //'photo_sizes[retina]' => '640x300',
    //'photo_sizes[iphone]' => '320x150', 
    'photo_sizes' => array( 'android' => '480x225',
                            'retina' => '640x300',
                            'iphone' => '320x150')
    );
 
  /*
  $data = 'title='.$post_title.'&content='.$post_content;
  $data .= '&photo=@header.jpg';
  $data .= '&photo_sizes[android]=480x225';
  $data .= '&photo_sizes[retina]=640x300';
  $data .= '&photo_sizes[iphone]=320x150';
  */
 
  $url = 'https://api.cloud.appcelerator.com/v1/posts/create.json?key='.$acs_app_key;
  $ch = curl_init($url);
 
  curl_setopt($ch, CURLOPT_COOKIEJAR, 'appccookie.txt');
  curl_setopt($ch, CURLOPT_COOKIEFILE, 'appccookie.txt');
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
  curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE); 
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
 
  curl_setopt($ch, CURLOPT_POST, TRUE);
  //curl_setopt($ch, CURLOPT_PUT, TRUE);
  curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
 
  $output = curl_exec($ch);
 
  var_dump($output);