Using mail() function to send mail with to , cc and bcc

$to       = 'ajeetkumar97@gmail.com'; 
$from     = 'ajeetkumardeveloper@gmail.com'; 
$bcc      = 'xyz@gmail.com'; 
$headers  = 'From:  ' . $_POST['firstname'] .' '.$_POST['lastname'].' <' . $from .'>' . " \r\n" ;
$headers .= "Content-type:text/html;charset=UTF-8" . "\r\n";
$headers .= "Bcc: $bcc\r\n";
$mail = '  
    

        
Appointment Registration
        
First Name
 
'.$_POST['firstname'].'
 
       
    
';
 mail($to,'Appointment Registration',$mail,$headers);