Warning: Cannot modify header information – headers already sent!
Info:
Posted in: Learned along the way
By: Blockcoder ( Admin ) / August 5th, 2011
Stats: 3 responses / Views: 174
Little sympathy
Okay first, i’m not going to explain what causes that warning message, but i’m explaining how to get rid of it. ( Because you don’t want to read so long story. )
Yes, i struggled with that problem for many hours and if I was frustrated with it, you are probably too.
Now, let us focus into the problem:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Your title</title>
</head>
<body>
<?php header( 'Location: http://www.blockcoders.net' ); ?>
</body>
<html>
Above, we are sending header information within our php or html code. In this simple example I want browser to take me to the index of blockcoders.net. And after this we are getting this frustrating warning message about header already sent!
Getting rid of it:
We can get rid of it by using ob_start(); and ob_flush(); -php functions. With these we are declaring WHEN we are sending the output buffers.
The warning message says: “headers already sent…” so if we flush output buffer AFTER we use header(); function ( and all of our other possible output data ), it will work:
//make sure HERE is no empty rows or any white space! <?php ob_start(); ?> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head></head> <body> <?php header( 'Location: http://www.blockcoders.net' ); ?> </body> </html> <?php ob_flush(); ?>
Make sure there are no white spaces at the beginning or at the end of your html or php code!
This was a really simplified example how to kick off the problem. BUT, I’m 100% sure that you won’t get that annoying warning message again!
Thanks folks, hope it helps 