Getting one’s HTTP headers in a twist
Published on 9th June 2007 Estimated Reading Time: 1 minuteI am in the process of further linking the content of hillwalking blog into the fabric of other parts of my website. To date, this has included adding a list of all the posts to the site map and a dossier of the latest entries to the site's welcome page. One thing that started to crop up were a series of warnings of the form:
Cannot modify header information - headers already sent by...
The cause of this was my calling a PHP script that was part of my hillwalking blog installation, and this caused Bad Behaviour to be invoked. The result was that an HTTP header was being sent to create a cookie after one already had been sent to display a web page. A spot of conditional coding and the use of an extra flag resolved the problem.
Apparently, there is another surefire way of getting the same result: whitespace before or after the <?php ... ?> tag in an included script. The cookie issue is one that I can understand, but it does seem strange that an attempt is made to send HTTP header information when the latter arises. It causes loads of questions, though...