Foreach无效语句仅适用于条件中的一种情况

我有一个表格,允许1到多个文件上传。我只是注意到,在提交多个文件时,会出现一个错误。

Invalid argument supplied for foreach()

对于这一行:

foreach ($filename as $indFile) {

文件会上载,但由于错误,它会影响文件中的其他区域。

只有在上传多个文件时才会显示此错误,这有什么错呢?

foreach ($_FILES as $file) {
    foreach($file['name'] as $key => $value) {
        if (!empty($value)) { //empty string
            if($file['error'][$key] != 4) { //error code is not #4
                $fu = new fileUpload();
                $filename = $fu->upload();
                $out = (count($filename) > 1 ? 'Multiple files were' : 'A file was'). '  uploaded. You can download ' . (count($filename) > 1 ? 'them' : 'the file'). ' from:</ul>';
                foreach ($filename as $indFile) {
                    $out .= "<li><a href='uploads/{$indFile}'>{$indFile}</a></li>";
                }
                $out .= '</ul>';
                $template = str_replace("{filename}", $out, $template);

                //echo "name is NOT empty AND error is NOT 4";
            } else { //error code IS #4
                //echo "error code is 4";
            }
        } else {
            //echo "name is empty!";
            $template = str_replace("{filename}", '', $template);
        }
    }
}
clearstatcache();