XML Parsing Error: xml processing instruction not at start of external entity

Question

I have a vBulletin 3.8 forum. When we click Edit button of any post (so the Quick Edit form should displayed), I get this error on the browser's console:

XML Parsing Error: xml processing instruction not at start of external entity Location: http://www.xxxxx.xx/ajax.php?do=quickedit&p=438 Row number 2, Column 1:

... the Quick Edit form is not appearing the the progress bar displayed permanently.

• I have try to disable hooks/ plugins, but the problem still appears.

• I have this row on config.php: ini_set("display_errors", false); so I don't think it is a fatal error/ warning by PHP which brokes the xml normal syntax.

• I have informed that this appear starts after the move of the site to another server. Does it say something to you?

Any general idea about this error?

EDIT: Well, I found the reason of this issue, but I don't know how to fix it. Exact the same site on a localhost testing board works perfectly, but on the live server ANY html page/ ajax call etc, has a useless empty line as line #1.

For normal html pages, there is no reason for the browser to return an error, but when we're talking about an ajax call, this empty line at the top of the response, breaks the xml parsing from the browser. So it seems it is a server/ PHP/ Apache setting that applies this empty line. Any idea how to fix it? https://i.stack.imgur.com/OInuC.jpg

Answer 1

It might be late for you but any new comers with php/nginx/apache can get an understanding of why.

Answer is simple: When moving the code, you might not be using git/rsync/scp but let me guess, you used zip (and probably Windows/Linux involved).

How to discover it was a two-day journey with many things tried:

We have the same error, we were also moving our servers. We tried:

• We thought the server software version was a problem.
• We thought the cloud provider OS image was a problem.
• We used docker to avoid these problems, but the empty line problem persists.
• We thought the code ?> ending was a problem, I went through all of them. But it wasn't.
• I finally asked my colleague: How did you get the code? From Git? He said he downloaded from ZIP and then uploaded to server.
• I removed code on the server (which extracted from a zip) and used git to download a fresh copy from our github.
• Magic, problem solved. The empty line gone.

So I think the problem is with the zipping progress might have changed some file empty lines. Always use git.