I have a PHP source file where  characters automatically got added in! I don't know from where they have come. I'm not getting any parse errors but it results in weird behavior in the execution of the file. E.g. header location functionality is not working sometimes! I'm curious how these kind of symbols are getting auto generated? I'm using UTF-8 encoding & the sign  is not showing in Notepad++ or Windows Notepad but with Netbeans IDE.
Eg. Code:
<?php
echo "no errors!";
header("Location: http://stackoverflow.com");
exit;
?>
What is this? How can I prevent it?
You propably save the files as UTF-8 with BOM. You should save them as UTF-8 without BOM.
It's called Byte Order Mark, and doesn't always have to be "". http://en.wikipedia.org/wiki/Byte_order_mark
Some Windows applications add BOM by default. In Notepad++ you can use some options in the Encoding menu like Encode in UTF without BOM or Convert to UTF without BOM.
I believe that whether you save it UTF-8 with or without BOM it still happens. I don't think it makes a difference.
Try it, see if it helps.
From a tool like vi or vim, you can modify and save the file without a BOM with the two following commands :
:setlocal nobomb
and then
:w
来源：https://stackoverflow.com/questions/18845976/whats-%c3%af-sign-at-the-beginning-of-my-source-file