我的错误日志因以下两个错误而失去控制

warning feof() expects parameter 1 to be resource

以及

warning fread() expects parameter 1 to be resource

负责的代码位是

<?php
    $file = '../upload/files/' . $filex;
    header("Content-Disposition: attachment; filename=" . urlencode($file));
    header("Content-Type: application/force-download");
    header("Content-Type: application/octet-stream");
    header("Content-Type: application/download");
    header("Content-Description: File Transfer");
    header("Content-Length: " . filesize($file));
    flush(); // this doesn't really matter.

    $fp = fopen($file, "r");
    while (!feof($fp)) {
        echo fread($fp, 65536);
        flush(); // this is essential for large downloads
    }
    fclose($fp);
?>

我用这个代码下载标题，但它现在吓坏了-之前有人问我已经尝试，我尝试谷歌，但仍然不完全理解错误信息。