PHP output MP4 video streaming function

function GetMp4File($file) { 
    $size = filesize($file); 
    header("Content-type: video/mp4"); 
    header("Accept-Ranges: bytes"); 
    if(isset($_SERVER['HTTP_RANGE'])){ 
        header("HTTP/1.1 206 Partial Content"); 
        list($name, $range) = explode("=", $_SERVER['HTTP_RANGE']); 
        list($begin, $end) =explode("-", $range); 
        if($end == 0){ 
            $end = $size - 1; 
        } 
    }else { 
        $begin = 0; $end = $size - 1; 
    } 
    header("Content-Length: " . ($end - $begin + 1)); 
    header("Content-Disposition: filename=".basename($file)); 
    header("Content-Range: bytes ".$begin."-".$end."/".$size); 
    $fp = fopen($file, 'rb'); 
    fseek($fp, $begin); 
    while(!feof($fp)) { 
        $p = min(1024, $end - $begin + 1); 
        $begin += $p; 
        echo fread($fp, $p); 
    } 
    fclose($fp); 
} 
GetMp4File("demo.mp4");