从命令行中删除变量时已经发送了PHP标头

So I have come to a veeeery weird thing about php logic.

I have made an htacces file like this:

RewriteEngine On
RewriteBase /gameplay/

RewriteRule ^((?!forums|bans|stats)[a-zA-Z0-9_-]+)$ index.php?p=$1
RewriteRule ^((?!forums|bans|stats)[a-zA-Z0-9_-]+)/$ index.php?p=$1

This makes sure that it converts all the strings in the first slashes in to php "p" variable, unless it is forums, bans or stats.

Weird part comes in when i try visiting the page.

Lets say that the url is http://domain.com/gameplay/news/ Everything is messed up, code shouts that header is sent there, there and everywhere else etc.

After I add a variable like this: http://domain.com/gameplay/news/?x=x or pretty much anything else, then it is completely fine and everything executes as it should...

Thanks in advance!