How to send a group of photos (gallery) to Telegram?

Question

PHP

Mobile galleries appeared in Telegram and the API was updated. The sendMediaGroup function appeared. Tell me
how to transfer photos there correctly?
Here is the sendphoto function performed as follows

$website="https://api.telegram.org/bot".$botToken;
$chatId = "19__9578"; //Receiver Chat Id 
    $file_name_with_full_path = realpath($full_path);
    $params=array(
    'chat_id'=>$chatId,
    'photo'     => '@'.$file_name_with_full_path,
    'caption'   => $caption,
    );
$ch = curl_init($website . '/sendPhoto');
curl_setopt($ch, CURLOPT_HEADER, false);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, ($params));
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
$result = curl_exec($ch);
curl_close($ch);

Where $full_path = ".\image.png" for example how to deal with group sending.
on the telegram site they write "pass "attach://" to upload a new one using multipart/form-data under name."
Is there an example? What t doesn't work.