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?