use the imap extension of php to receive qq messages as follows:

$mailbox = "{imap.qq.com:993/imap/ssl} INBOX";
$username = "qq ";
$password = "qq ";
$res = imap_open($mailbox , $username , $password);
// 
$count = imap_num_msg($res);
var_dump($count);

the above code reported an error:

Why is this?