Hello, meanwhile Alessandro will add this feature, i wrote this function to add hreflang inside <head> tag, this work for me, if you want try, put it into functions.php of your theme
function add_hreflang()
{
global $wpCeceppaML;
$current = CMLLanguage::get_default();
$MYurl = cml_get_the_link($current->cml_language_slug);
if(cml_is_homepage($MYurl))
{
$frontpage_id = get_option('page_on_front');
$homelang = CMLPost::get_language_slug_by_id($frontpage_id);
if($homelang != $current->cml_language_slug)
{
$postid = CMLPost::get_translation($current->cml_language_slug, $frontpage_id);
}
else $postid = $frontpage_id;
}
else $postid = cml_get_page_id_by_path($MYurl);
$head_link = "";
$alternate = CMLPost::get_translations($postid);
if(sizeof($alternate["linked"]))
{
$original_link = preg_replace( "/\?lang.*/", "", $MYurl);
$head_link .= '<link rel="alternate" hreflang="'.CMLLanguage::get_default_slug().'" href="'.$original_link.'" />';
foreach($alternate["linked"] as $key=>$value)
{
$link = get_permalink($value);
$head_link .= '<link rel="alternate" hreflang="'.$key.'" href="'. $wpCeceppaML->convert_url($link, $key ) .'" />';
}
}
echo $head_link;
}
add_action('wp_head', 'add_hreflang');