upload in metabox

Hello,
I added own metabox for upload in flamingo. I try catch POST and FILES data, but no work. Can i help me please? Thank you.

function save_custom_meta_data($id) {
    file_put_contents('data.log',print_r($_POST,true));
    file_put_contents('files.log',print_r($_FILES,true));
}
add_action('save_post', 'save_custom_meta_data');