I'm trying to create a filter and it seem to be working when I view the postings but when I go to the admin page and save a change I get an warning about not being able to modify header information
Warning: Cannot modify header information - headers already sent by (output started at /xxxxxxxxxx/wordpress/wp-content/plugins/jimagetags.php:55) in /xxxxxxxxxx/wordpress/wp-includes/pluggable.php on line 770
But I can't figure out what I'm doing wrong, does anyone have a suggestion what kind of error I should be looking for? Please note that I'm completely new to writing stuff for WP so I'm probably missing something really basic.