'headers already sent' error with php redirect

[IanS]

Back again with same task but moved on half a step.Trying to redirect to mobile page using php.I assumed the code here would redirect if the match was true, or continue to load the page (index.php) if not. <?php $agent = $_SERVER['HTTP_USER_AGENT']; if(preg_match('/iPhone|Android|Blackberry/i', $agent)){ header("Location: mobile.html"); exit; } ?>But is there some boolean weirdness? I'm getting this error - Warning: Cannot modify header information - headers already sent by (output started at /mysite/index.php:1) in /mysite/index.php on line 4index.php on line 4?(If the match isn't true (not a mobile device) the page (index.php) loads ok.)

 

[justsomeguy]

That error means it can't send the header because it already sent output, which causes all headers to go out. The output started on index.php at line 1. If you have that file saved as a UTF file, make sure to save it without the BOM.

[IanS]

That was it.

 

Works now

 

So folks are happy, and I'm off to buy some necessary books.

Thanks

 

(I remember that from when I first set up a phpbb forum ages ago and had a non-functioning site. If I'd understood the error I might have remembered it.)