在video.php上添加曲目（字幕）

我已经创建了这个代码，通过Ios播放一些视频，播放方法是成功的

我需要添加标题或一些东西来显示曲目（字幕）。vtt何时开始播放

我的代码是：

<?php
header('Access-Control-Allow-Origin: *');
include("engine/config.php");



$id=$_GET['ssid'];
$sel = mysql_query("select * from movies where id='$id'");
$num = mysql_num_rows($sel);

if($num == 1){
    //get info
  $row = mysql_fetch_assoc($sel);


  $mov_up = $row['mov_up'];
  $play=$mov_up;

    $path=substr($play,0,13);   
$key1=substr($play,13,8);
$key2=substr($play,21,8);
$key3=substr($play,29,8);   

$fullpath= $path.$key3.$key1.$key2;

$play=$store.$fullpath;

@fread($file);
$file = $play;
$fp = @fopen($file, 'rb');



$size   = filesize($file); // File size
$length = $size;           // Content length
$start  = 0;               // Start byte
$end    = $size - 1;       // End byte

header('Content-type: video/mp4');
header("Accept-Ranges: 0-$length");
if (isset($_SERVER['HTTP_RANGE'])) {

    $c_start = $start;
    $c_end   = $end;

    list(, $range) = explode('=', $_SERVER['HTTP_RANGE'], 2);
    if (strpos($range, ',') !== false) {
        header('HTTP/1.1 416 Requested Range Not Satisfiable');
        header("Content-Range: bytes $start-$end/$size");
        exit;
    }
    if ($range == '-') {
        $c_start = $size - substr($range, 1);
    }else{
        $range  = explode('-', $range);
        $c_start = $range[0];
        $c_end   = (isset($range[1]) && is_numeric($range[1])) ? $range[1] : $size;
    }
    $c_end = ($c_end > $end) ? $end : $c_end;
    if ($c_start > $c_end || $c_start > $size - 1 || $c_end >= $size) {
        header('HTTP/1.1 416 Requested Range Not Satisfiable');
        header("Content-Range: bytes $start-$end/$size");
        exit;
    }
    $start  = $c_start;
    $end    = $c_end;
    $length = $end - $start + 1;
    fseek($fp, $start);
    header('HTTP/1.1 206 Partial Content');
}
header("Content-Range: bytes $start-$end/$size");
header("Content-Length: ".$length);


$buffer = 1024 * 8;
while(!feof($fp) && ($p = ftell($fp)) <= $end) {

    if ($p + $buffer > $end) {
        $buffer = $end - $p + 1;
    }
    set_time_limit(0);
    echo fread($fp, $buffer);
    flush();
}

fclose($fp);
exit();


}


?>