Sending Attachment through PHP mail function

Sending Attachment using mail() function :
   // request variables // important
   $from = $_REQUEST["from"];
   $emaila = $_REQUEST["emaila"];
   $filea = $_REQUEST["filea"];
 
   if ($filea) {
      function mail_attachment ($from , $to, $subject, $message, $attachment){
         $fileatt = $attachment; // Path to the file
         $fileatt_type = "application/octet-stream"; // File Type
       
         $start = strrpos($attachment, '/') == -1 ?
            strrpos($attachment, '//') : strrpos($attachment, '/')+1;

         $fileatt_name = substr($attachment, $start,
            strlen($attachment)); // Filename that will be used for the
            file as the attachment
       
         $email_from = $from; // Who the email is from
         $subject = "New Attachment Message";
       
         $email_subject =  $subject; // The Subject of the email
         $email_txt = $message; // Message that the email has in it
         $email_to = $to; // Who the email is to
       
         $headers = "From: ".$email_from;
         $file = fopen($fileatt,'rb');
         $data = fread($file,filesize($fileatt));
         fclose($file);
       
         $msg_txt="\n\n You have recieved a new attachment message from $from";
         $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_txt .= $msg_txt;

         $email_message .= "This is a multi-part message in MIME format.\n\n" .
            "--{$mime_boundary}\n" . "Content-Type:text/html;
            charset = \"iso-8859-1\"\n" . "Content-Transfer-Encoding: 7bit\n\n" .
            $email_txt . "\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);
       
         if($ok) {
            echo "File Sent Successfully.";
            unlink($attachment); // delete a file after attachment sent.
         }else {
            die("Sorry but the email could not be sent. Please go back and try again!");
         }
      }
      move_uploaded_file($_FILES["filea"]["tmp_name"],
         'temp/'.basename($_FILES['filea']['name']));

      mail_attachment("$from", "youremailaddress@gmail.com",
         "subject", "message", ("temp/".$_FILES["filea"]["name"]));
   }
?>