PHP上传csv文件-上传后格式无效

我目前正在php的帮助下上传文件到文件系统。具体来说，我正在使用csv扩展文件。我能够获得存储在名为csv_uploads的文件夹中的文件，并为其分配一个唯一的名称。问题是文件保存在以.1作为文件扩展名的目录中，因此失去了csv扩展名。这种行为的原因是什么?

    header('Content-Type: text/plain; charset=utf-8');
    try {
        // Undefined | Multiple Files | $_FILES Corruption Attack
        // If this request falls under any of them, treat it invalid.
        if (
            !isset($_FILES['upfile']['error']) ||
            is_array($_FILES['upfile']['error'])
        ) {
            throw new RuntimeException('Invalid parameters.');
        }
        // Check $_FILES['upfile']['error'] value.
        switch ($_FILES['upfile']['error']) {
            case UPLOAD_ERR_OK:
                break;
            case UPLOAD_ERR_NO_FILE:
                throw new RuntimeException('No file sent.');
            case UPLOAD_ERR_INI_SIZE:
            case UPLOAD_ERR_FORM_SIZE:
                throw new RuntimeException('Exceeded filesize limit.');
            default:
                throw new RuntimeException('Unknown errors.');
        }
        // You should also check filesize here.
        if ($_FILES['upfile']['size'] > 1000000) {
            throw new RuntimeException('Exceeded filesize limit.');
        }
        // DO NOT TRUST $_FILES['upfile']['mime'] VALUE !!
        // Check MIME Type by yourself.
        $finfo = new finfo(FILEINFO_MIME_TYPE);
        if (false === $ext = array_search(
            $finfo->file($_FILES['upfile']['tmp_name']),
            array(
                'text/csv',
                'text/plain',
                'application/csv',
                'text/comma-separated-values',
                'application/excel',
                'application/vnd.ms-excel',
                'application/vnd.msexcel',
                'text/anytext',
                'application/octet-stream',
                'application/txt'
            ),
            true
        )) {
            throw new RuntimeException('Invalid file format.');
        }
        // You should name it uniquely.
        // DO NOT USE $_FILES['upfile']['name'] WITHOUT ANY VALIDATION !!
        // On this example, obtain safe unique name from its binary data.
        if (!move_uploaded_file(
            $_FILES['upfile']['tmp_name'],
            sprintf('./csv_uploads/%s.%s',
                sha1_file($_FILES['upfile']['tmp_name']),
                $ext
            )
        )) {
            throw new RuntimeException('Failed to move uploaded file.');
        }
        echo 'File is uploaded successfully.';
    } catch (RuntimeException $e) {
        echo $e->getMessage();
    }