使用php将电子邮件发送到多个地址

It only sends email to the first email address. The second email address does not work because it is a variable. What do you think?

  $to = "email1@gmail.com,". $rs['email2'];
    $subject = "Hello";
    $from = "admin@itservice.com";
    $headers = "From: $from
";
    $headers .= "MIME-Version: 1.0
"
      ."Content-Type: multipart/mixed; boundary=\"1a2a3a\"";


    $message .= "This is a message..."
      ."--1a2a3a
";

    $file = file_get_contents("memomemomemo4.pdf");



    // Send email

      $success = mail($to,$subject,$message,$headers);

Try this syntax instead:

$to = "email1@gmail.com,".$rs['email2'];

Why not:

$rs['email2'] = "me@me.com";
echo "email1@gmail.com,{$rs['email2']}";
# email1@gmail.com,me@me.com