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();