why does PHP fopen + fwrite double document?

I am running PHP Version 5.3.4 with Apache/2.2.17 on Windows 7 Ultimate 32bit (IIS disabled). I been looking at the fopen modes and am well aware of what mode does what, but i can't wrap my finger around why the double posting to the txt file with a single fwrite. I've even tried modes: w and c.

Now I don't care whether the new data coming in is being prepend or appended, just so long as its there in the file without truncating existing data.

The real question is, why does the "a" mode instead of just appending new data, it writes (duplicates) the new data to the file twice before it closes.

In php code:

$fh = "";
if(!($fh = fopen("list.txt","x")) // if file exists, just open for writing (prepend)
   $fh = fopen("list.txt","a"); // if not exist, open just for writing (append)

fwrite($fh,"Somthing\r\n开发者_如何学运维"); // write to file (filehandle, "data")
fclose($fh); // close the file

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Results:

Somthing

Somthing

SOLVED: Found the culprit: nothing was wrong with my coding. It was an html validator extension I used for Chromium under Ubuntu 10.04. This extension was apparently causing something similar to instant page reload.

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$fh = fopen("list.txt","a");
fwrite($fh,"Somthing\n"); // write to file (filehandle, "data")
fclose($fh); // close the file

your logic was not correct.

that's how its done, i hope it works for you

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I appreciate that this is years old but this problem is still known to occur and there is another reason that may also cause it. I didn't have the extension used by @robx, disabled all my extensions and no change - still double entries. However, after reading this thread about it being a Chrome bug (https://bugs.chromium.org/p/chromium/issues/detail?id=64810) comment 16 suggests the issue is the favicon being prefetched. Not ideal but delete the favion icon link tag in the head of the document and it stops double entries.