Something

$fileatt = "/path/to/file.doc";
$fileatt_type = "application/octet-stream"; // File Type
$fileatt_name = "file.doc"; // Filename that will be used for the file as the attachment

$email_from = ""; // Who the email is from
$email_subject = ""; // The Subject of the email
$email_txt = ""; // Message that the email has in it

$email_to = ""; // Who the email is too

$headers = "From: ".$email_from;

$file = fopen($fileatt,'rb');
$data = fread($file,filesize($fileatt));
fclose($file);

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

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

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

$data = chunk_split(base64_encode($data));

$email_message .= "--{$mime_boundary}\n" .
                  "Content-Type: {$fileatt_type};\n" .
                  " name=\"{$fileatt_name}\"\n" .
                  //"Content-Disposition: attachment;\n" .
                  //" filename=\"{$fileatt_name}\"\n" .
                  "Content-Transfer-Encoding: base64\n\n" .
                 $data . "\n\n" .
                  "--{$mime_boundary}--\n";

$ok = @mail($email_to, $email_subject, $email_message, $headers);