Thanks so much Danny for your help. It works !
How do you add the first name and last name, I tried this but it didn’t work and couldn’t find any doc online :
$api->add_list_member( $list_id, [ “email_address” => “[email protected]”, “status” => “subscribed”, “FNAME” => “John”, “LNAME” => “Markus” ]);
Thanks in advance for your help