PHP下载封装

function download($has_name, $has_size, $file_name)
{
    ob_end_clean();
//用以解决中文不能显示出来的问题
    $file_name = iconv("utf-8", "gb2312", $file_name);
    $file_sub_path = $_SERVER['DOCUMENT_ROOT'] . "/Download/";
    $file_path = $file_sub_path . $file_name;
//首先要判断给定的文件存在与否
    if (!file_exists($file_path)) {
        echo "没有该文件文件:" . $file_path;
        return;
    }
    $fp = fopen($file_path, "rb");
    $file_size = filesize($file_path);
//下载文件需要用到的头
    Header("Content-type: application/octet-stream");
    Header("Accept-Ranges: bytes");
    if ($has_size) {
        Header('Content-Length: ' . $file_size);
        Header("Accept-Length:" . $file_size);
    }
    if ($has_name) {
        Header("Content-Disposition: attachment; filename=" . $file_name);
    }
    $buffer = 1024;
    $file_count = 0;
//向浏览器返回数据
    while (!feof($fp) && $file_count < $file_size) {
        $file_con = fread($fp, $buffer);
        $file_count += $buffer;
        echo $file_con;
    }
}

遇到问题，最初下载正常，APK文件，但几天后开始下载 后APK无法解析，发现必须加上

ob_end_clean();