Email with attachment - PHP

$files = "logo.jpg";
// email fields: to, from, subject, and so on
$to = "example@example.com";
$from = "example@example.com";
$subject ="Test";
$message = "My message";
$headers = "From: $from";

// boundary
$semi_rand = md5(time());
$mime_boundary = "==Multipart_Boundary_x{$semi_rand}x";

// headers for attachment
$headers .= "\nMIME-Version: 1.0\n" . "Content-Type: multipart/mixed;\n" . " boundary=\"{$mime_boundary}\"";

// multipart boundary
$message = "This is a multi-part message in MIME format.\n\n" . "--{$mime_boundary}\n" . "Content-Type: text/html; charset=\"iso-8859-1\"\n" . "Content-Transfer-Encoding: 7bit\n\n" . $message . "\n\n";
$message .= "--{$mime_boundary}\n";

// preparing attachments
   
$file = fopen($files,"rb");
$data = fread($file,filesize($files));
fclose($file);
$data = chunk_split(base64_encode($data));
$message .= "Content-Type: {\"application/octet-stream\"};\n" . " name=\"$files\"\n" .
"Content-Disposition: attachment;\n" . " filename=\"$files\"\n" .
"Content-Transfer-Encoding: base64\n\n" . $data . "\n\n";
$message .= "--{$mime_boundary}-\n";

// send

$ok = @mail($to, $subject, $message, $headers);
if ($ok) {
    echo "<p>mail sent to $to!</p>";
} else {
    echo "<p>mail could not be sent!</p>";
}