問題描述
我想知道名為 MAX_FILE_SIZE 的隱藏字段應該如何工作?
I am wondering how is the hidden field named MAX_FILE_SIZE supposed to work?
<form action="" method="post" enctype="multipart/form-data">
<!-- in byes must preceed file field -->
<input type="hidden" name="MAX_FILE_SIZE" value="2097152" />
<input type="file" name="upload" />
<input type="submit" name="submit" value="Submit" />
</form>
我上傳了一個 4MB 以上的文件，但我沒有收到來自客戶端的警告(我不是在談論服務器端).MAX_FILE_SIZE 應該做什么?
I uploaded a 4MB+ file but I got no warning from client side (I am not talking about server side). What is it MAX_FILE_SIZE supposed to do?
更新
好的，所以 PHP 強加了一個軟"限制.但是使用它和檢查諸如 $_FILES['upload']['size'] < 之類的東西有什么區別嗎?2000 在代碼中?
OK so its for PHP to impose a "soft" limit. But is there any difference between using it and checking something like $_FILES['upload']['size'] < 2000 in code?
推薦答案
MAX_FILE_SIZE 是 KB 而不是 字節.你是對的，它以字節為單位.因此，對于 4MB 以字節為單位轉換 4MB {1024 * (1024 * 4)} 的限制，請嘗試:
MAX_FILE_SIZE is in KB not bytes. You were right, it is in bytes. So, for a limit of 4MB convert 4MB in bytes {1024 * (1024 * 4)} try:
<input type="hidden" name="MAX_FILE_SIZE" value="4194304" />
正如其他人所解釋的那樣，您永遠不會收到警告.它只是在服務器端強加一個軟限制.
As explained by others, you will never get a warning for this. It's there just to impose a soft limit on server side.
回答您的子問題.是的，有區別，您永遠不要相信用戶輸入.如果您想始終施加限制，則必須始終檢查其大小.不要相信 MAX_FILE_SIZE 的作用，因為它可以由用戶更改.所以，是的，您應該檢查以確保它始終達到或超過您想要的尺寸.
To answer your sub-question. Yes, there is a difference, you NEVER trust the user input. If you want to always impose a limit, you always must check its size. Don't trust what MAX_FILE_SIZE does, because it can be changed by a user. So, yes, you should check to make sure it's always up to or above the size you want it to be.
不同之處在于，如果您將 MAX_FILE_SIZE 強加為 2MB，并且用戶嘗試上傳 4MB 的文件，一旦達到大約上傳的前 2MB，傳輸將終止，PHP 將停止接受該文件的更多數據.它將報告文件數組的錯誤.
The difference is that if you have imposed a MAX_FILE_SIZE of 2MB and the user tries to upload a 4MB file, once they reach roughly the first 2MB of upload, the transfer will terminate and the PHP will stop accepting more data for that file. It will report the error on the files array.
這篇關于HTML 上傳 MAX_FILE_SIZE 似乎不起作用的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！