PHP文件上载错误（UPLOAD_ERR_PARTIAL）/ $ _FILES为空或具有空“tmp_name”

Question

I have a quite common problem and spent hours to read some things about it, but I don't manage to fix it and I'm going crazy...

Context

I have a website where users can upload a picture to my server (from iOS / Safari browser in the common case). The page with the upload form is this one .

The backend is made with PHP (no framework). Front-end is HTML / Javascript. This is a quite old site I've made in 2010 so this is not "super sexy"! :-)

I made logs to monitor upload results, and I see that about 30% of user uploads failed ... I guess this is not usual!

These errors are from 2 origins (same user trying to upload several times can have a mix of these 2 origins) :

• $_FILES['myFormFieldName'] is NULL
• $_FILES['myFormFieldName'] is NOT NULL but $_FILES['myFormFieldName']['error'] is 3 ( UPLOAD_ERR_PARTIAL ) with $_FILES['xxx']['tmp_name'] and $_FILES['xx']['type'] empty and $_FILES['xxx']['size'] is "0"

These errors appears not to be deterministic...

• When I test myself (using the same image than a user having problems with uploading it) I have no problems
• I see in my logs that some users semms to always have problems with upload, but other don't.
• I also see that some users having problems managed to upload their file with siccess after several retry
• I had contact with one user having problems saying that he has the Safari cannot open the page because network connection was lost error page from Safari when trying to upload its picture (whenever he is in WiFi or mobile 3G/4G data)

---

Code

HTML of form to upload the file (limit the user uploads to 35M from client-side)

    <ul class="pageitem">
        <form name="empty-custom-native" 
              enctype="multipart/form-data" 
              action="/upload.php?method=nativeUpload" 
              method="post">
            <input type="hidden" name="MAX_FILE_SIZE" value="36700160" />
            <li class="button" >
                <input type="file" name="iosImageFILE" id="iosImageFILE"/>
            </li>
        </form>
        <li class="button directUrlButton" onclick="javascript:onclickNativeUploadForm();">
            <input type="button" value="Upload" />
        </li>
    </ul>

Javascript called by HTML (used to check that the file input is not empty before submit the form)

  function onclickNativeUploadForm(){
    if( document.getElementById('iosImageFILE').value=="" ){
      alert("Please choose an image FIRST !");
    } else{
      showPleaseWait();
      setTimeout(submitNativeUploadForm, 2000);
    }
  }

  function submitNativeUploadForm(){
      document.forms['empty-custom-native'].submit();
  }

PHP code managing the file upload (extract)

<?php
if( isset($_FILES['iosImageFILE']) && !empty($_FILES['iosImageFILE']) ){
    $uploadStatus = $_FILES['iosImageFILE']['error'];
    if( $uploadStatus==0 ){
        // Copy source file to temp file
        if( !move_uploaded_file($_FILES['iosImageFILE']['tmp_name'], $_SERVER['DOCUMENT_ROOT']."/".$userImageTemp) ) {
            throw new Exception("fileUploadCopy");
        }

    } else{
        if( $uploadStatus==1 ){ throw new Exception("fileUploadIniSize"); }
        else if( $uploadStatus==2 ){ throw new Exception("fileUploadFormSize"); }
        else if( $uploadStatus==3 ){ throw new Exception("fileUploadPartial"); } // THIS ERROR ...
        else if( $uploadStatus==4 ){ throw new Exception("fileUploadNoFile"); }
        else if( $uploadStatus==6 ){ throw new Exception("fileUploadNoTmpDir"); }
        else if( $uploadStatus==7 ){ throw new Exception("fileUploadCantWrite"); }
        else if( $uploadStatus==8 ){ throw new Exception("fileUploadExtension"); }
        else{
            throw new Exception("fileUploadSystem");
        }
    }
} else{
    throw new Exception("fileUploadUpload"); // ... OR THIS ERROR
}

// If anything was OK, we continue here with the uploaded file copied in our working dir to do some stuff with it...
?>

So in my case I have fileUploadUpload or fileUploadPartial exceptions.

---

Investigations

Server-side (php.ini config)

I've checked the PHP environment variables dealing with file upload (with ini_get command) to check that I didn't exceed the max file size or max uploads number.

Everything seems fine, I have quite generous limits, post_max_size is gretaer than upload_max_filesize . upload_tmp_dir is empty by I guess this means that I use the default system /tmp dir?

Tell me if you see problems or other things to check.

Note: I don't have access to php.ini , but these values are fixed by my hosting provider (I am on a shared hosting).

file_uploads : '1'
upload_tmp_dir : ''
upload_max_filesize : '128M'
max_file_uploads : '20'
post_max_size : '130M'
max_execution_time : '300'

Client-side (HTML/JS code)

MAX_FILE_SIZE is less than the max file size allowed by my PHP server.

I used enctype="multipart/form-data" and method="post" as expected.

I don't do AJAX file upload, just using Javascript to check input file emptiness before submit the form with JS.

Server-side (PHP code)

When I debug the content of $_FILES['iosImageFILE'] I get this for the fileUploadPartial error (and this is null for the fileUploadUpload error).

iosImageFILE = {"name":"DD292A1C-9CBF-4843-9E1C-7C815593C67A.png","type":"","tmp_name":"","error":3,"size":0}

Server-side (filesystem)

I tried to check the /tmp directory where the uploaded files are supposed to be, but I don't have access to it. I would like to check that it is not "full of old tmp files" but I guess not.

Indeed I made a PHP script to scan its content using var_export(scandir('/tmp')) and I only see some sess_xxxxx session files (about 7000 files).

Code upgrade

I've upgraded and enhanced my website to be in https (was non secured http before) and upgrade PHP version from 5.6 to 7.0). Without any change on file upload problems.

Firewall ?!?

I perhaps suspect a firewall problem with my hosting provider (I've read that it could block some things about file upload...). But they said me that there is no firewall activated on my host...

---

Conclusion

I really don't know what to check next to investigate and find this problem.

Please note that almost everybody uploading files comes from iOS / Safari browser. I don't know if there would be the same problems from other OS or browsers...

I'm a front-end web developer and I must admint I'm not comfortable with this kind of problem.

Any help appreciated!

Answer 1

End of the story : as suspected, this was a problem with my hosting provider (they took 1 month to solve it...)

I didn't managed to get more details, except that it was an "Apache configuration problem", and that it has a link with load balacing...