CODEWITHSUNDEEP
phpajaxfile-uploadmultipartform-datafine-uploader
Nick F
Nick F

Reputation: 10122

File upload script apparently not executing until upload has completed

I have an odd problem: I've got an AJAX file uploader (fineuploader, as it happens), with a server-side script (PHP) that handles the upload. Although the uploader has an "allowedExtensions" setting, I want the allowed extensions to be specified on the server side, so my upload handler checks the file extension and returns an error response if the file's extension is not allowed.

The problem I'm having is that whereas in my dev environment the upload handler returns this response straight away (as expected) and the upload stops, on another server the upload goes ahead and the response is only returned after the upload has completed. Which potentially means a very long wait before receiving an error message.

Looking at the network info in developer tools, it seems the browser is waiting for a response the whole time, and (on the problematic server) only receives it after the upload has completed, which seems to suggest that on the server the upload handler script is actually not being executed until after all the data has been received.

It seems to me that the most likely culprit is some setting to do with how PHP handles uploads / multi-part form data, but I can't figure out what that might be. Would be grateful for any advice!

Update:

It seems the problem is the same on both servers (I just didn't notice the lag on one). So it seems my upload handler script is not executing until the file transfer has completed (this seems likely because the script checks the filename early on and throws an Exception if the extension is wrong, so it should respond quickly once it's started. Also, it always responds almost immediately when the upload has completed - however long that takes - suggesting that's when it's being executed).

Is this just a feature of how PHP handles multi-part form data? Is there any way of allowing the script to respond immediately if the filename is unsuitable?

Upvotes: 1

Views: 209

Answers (1)

Mathieu Dumoulin
Mathieu Dumoulin

Reputation: 12244

It could be as simple as the dev server being really fast to receive the file and respond as fast. If the dev server is on your own machine or a local dev server, 100mbits connexion makes even the pretty large file blazingly fast while on a production server that is often outside of the current network, the upload is long...

Sadly no, it's not possible for PHP to respond before the request being complete because thats the very nature of HTTP. You can cut off the connection once the request is sent and not read the response but you can't expect to receive a response until the whole request is sent. Although i used to do this with my friends, that is cut them off and answer before the end of the question, i can ensure you that only humans are capable of that feat! Oh and dont do that, it breaks friendships

o multipart doesn't mean chunked upload, it means the message is separated into different parts using a message boundary to separate the different element. If the process started before the whole request was sent anyway, you'd need to integrate mechanisms to detect if a certain part of your request was completely uploaded which would make the web even harder to program than it is now!

You can look at this for an example of what a multipart request looks like htmlcodetutorial.com/forms/form_enctype.html

Upvotes: 2

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