attached files are wrong... sometimes

Question

As a beginner i created this code

$o1 = $_POST['pliki'];
            $o12 = $_POST['pliki2'];

            $o2 = $_POST['o2'];
            $o22 = $_POST['o22'];


            $tab1 = explode(',', $o1);
            $tab12 = explode(',', $o12);

            $tab2 = explode(',', $o2);
            $tab22 = explode(',', $o22);

            if(isset($o2) && (bool) $o2) {  


                $format_wydruku1=$_POST['format_wydruku1'];
                $format_wydruku2=$_POST['format_wydruku2'];




                $to = "[email protected]";

                $from = "[email protected]";
                $subject ='Zamówienie od '.$imie.' '.$nazwisko;
                $message = "\n\n";




                $tab111=array_merge($tab1, $tab12);
                $tab222=array_merge($tab2, $tab22);

                for($i = 0; $i<count($tab111); $i++) {
                   $plik2 = "../upload/";
                    $plik2 .= $tab222[$i];


                    $name2 = $tab111[$i];
                    if($i<count($tab1)){
                        $message .= $name2."  ilosc kopii: ".$ile1."   format wydruku:".$format_wydruku1."\n";
                    }else if($i>=count($tab1)){
                        $message .= $name2."  ilosc kopii: ".$ile2."   format wydruku:".$format_wydruku1."\n";
                    }
                }



                /////////////////////////////////////////////////////////////////////////
                $headers = "From: $from";
                $semi_rand = md5(time());
                $mime_boundary = "==Multipart_Boundary_x{$semi_rand}x";

                //$headers .="Content-type: text/html; charset=utf-8";
                $headers .= "\nMIME-Version: 1.0\n" . "Content-Type: multipart/mixed;\n" . " boundary=\"{$mime_boundary}\"";


                $message = "This is a multi-part message in MIME format.\n\n" . "--{$mime_boundary}\n" . "Content-Type: text/plain; charset=\"iso-8859-1\"\n" . "Content-Transfer-Encoding: 7bit\n\n" . $message . "\n\n";
                $message .= "--{$mime_boundary}\n";
                $FfilenameCount = 0;


               for($i = 0; $i<count($tab111); $i++) {
                    if($i<count($tab1)){
                        $plik = "../upload/";
                        $plik .= $tab2[$i];

                        $afile = @fopen($plik,"rb");
                        if(empty($afile)){
                            continue;
                        }


                        $data[i] = @fread($afile,filesize($plik));
                        @fclose($afile);

                        $data[i] = chunk_split(base64_encode($data[i]));
                        $name = $tab111[$i];

                        $message .= "Content-Type: {\"application/octet-stream\"};\n" . " name=\"$name\"\n" .
                            "Content-Disposition: attachment;\n" . " filename=\"$name\"\n" .
                            "Content-Transfer-Encoding: base64\n\n" . $data[i] . "\n\n";
                        $message .= "--{$mime_boundary}\n";
                    }else if($i>=count($tab1)){
                        $plik = "../upload/";
                        $plik .= $tab222[$i];

                        $afile = @fopen($plik,"rb");
                        if(empty($afile)){
                            continue;
                        }


                        $data[i] = @fread($afile,filesize($plik));
                        @fclose($afile);

                        $data[i] = chunk_split(base64_encode($data[i]));
                        $name = $tab111[$i];

                        $message .= "Content-Type: {\"application/octet-stream\"};\n" . " name=\"$name\"\n" .
                            "Content-Disposition: attachment;\n" . " filename=\"$name\"\n" .
                            "Content-Transfer-Encoding: base64\n\n" . $data[i] . "\n\n";
                        $message .= "--{$mime_boundary}\n";
                    }
               }

                if(mail($to, $subject, $message, $headers)) {
                    echo '<p>Sent</p>';

                } else {
                    echo "<p>error, try again!</p>";
                }
            }else{

which sends chosen files with some additional informations. It is working, but... sometimes it sends right files, sometime not... have no idea how to fix it, and where exactly problem is. Names of attached are alway right...