[RESOLVED] any way to tell if headers have been sent?

sneakyimp

is there any way to determine if characters have been echoed to the browser? i have a function that will want to redirect to a nice neat error page if nothing has been output yet and would like to detect if i can use header() or have to echo a META REFRESH tag.

thorpe

If you looked at the manual entry for the [man]header/man function you would have noticed there is a see also section. Here you would find a link the the [man]headers_sent/man function.

sneakyimp

i had seen that but was wondering if sending another kind of header() call would have set that to true. what i'm really trying to test is whether any text has actually been output. apparently headers only get sent when you actually echo something to the client as demonstrated.

$hs1 = headers_sent();
header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
$hs2 = headers_sent();
echo "headers sent 1:" . $hs1 . "<br>";
$hs3 = headers_sent();
echo "headers sent 2:" . $hs2 . "<br>";
echo "headers sent 3:" . $hs3 . "<br>";

output:

headers sent 1:
headers sent 2:
headers sent 3:1

Weedpacket

That's right. The headers aren't sent the instant header() is called: they're collected up and then sent all together (either immediately before output or, if there wasn't any output, at the end of the script). Buffering can also have an effect; there may be a gap between the output being generated and the output actually being sent (flush() will override this behaviour at least at PHP's level). It's a matter of trying to fill tcp packets efficiently.

And since all http responses have headers, it doesn't matter if header() or any other header-generating function is called or not: there will be headers and they will need to be sent at some point.